Since 5gen wrote his thoughts, I gonna do the same :
Suspect worthy :
Mushy is certainly the more broken thing which stands in ZU right now. Bugnium Z, CM Barrier, CM Z-Heal bell, classical Mushyny... are all so effective to make trouble to the opposite team. If every single set it runs have counters, it's impossible to know in advance what it took as moves. Without Dark types, the CM Barrier Stored set 6-0 whole team only at the team preview. Its supposed passivity hide the fact that this dream eater loves wearing a Z-Move which removes whatever mon who could deal with stuff like trick, taunt, encore. If you thought run a dark type like shiftry or pawniard was enough to prevent to be swept, you will be really disappointed to know that Bugnium Z/Fairium Z is a thing and it OHKO both of them at +1. You need several answers in a team to be able to bypass it which restricts hugely the teambuilding. And if all that wasn't enough to convince you, let me say that Mushy doesn't need a particular support to work, it's very splashable and can be incorporate in any team you wish.
I noticed a lot of people don't understand why frosttom is suspect worthy so I would like to clarify the reasons why a large part of the community thinks it could be suspected.
The first thing I wanna say is Rotom-Frost is indeed not broken. It has common ways to deal with as revenge killing it with faster scarfs or counter or check it with various answer. Without trick, it's unable to beat in 1vs1 stuff like grumpig, chinchou, seaking, probopass, regice, muk, bronzor,... With trick, it's more annoying to kill it with defensive answers in 1vs1 but it is not still broken.
So why do we think it will be a good idea to suspect frosttom if it is not broken ? Because it is unhealthy and overcentralizing.
Unhealthy because fight against Rotom-Frost is a story of 50/50 always in its favor. Blizzard or Volt Switch ? Trick or Icium Z ? Pain Split or Substitute ? If you answered wrong, you lose one mon. If you answer right at all the 50/50, congratulation, you have weaken frosttom or gain the momentum. The situation isn't only totally unbalanced, the situation is also based on chance and required none skills. A decision completely rationnal is impossible to take if you didn't receive the pastebin of the opposite team just before. For example, a combinaison of Frosttom icium-z and Stoutland Band Pursuit cannot be rationnaly anticipated and a lot of players will lose stupidly their grumpig in believing it's a good answer to frosttom whatever it does. Same with muk, you thought it was a good frosttom switch-in due to its high special bulk and sticky hold but did you know Icium-Z + Blizzard remove 80% of your life ? You should.
And that's why Frosttom is overcentralizing. A lot of people think that overcentralizing mean the mon suspected is too much played. That's false, overcentralizing means the metagame is too much centralized around the banworthy mon, here Rotom-Frost. To prevent the stories above with the fridge clicks without pressure volt-switch and then send a physical wallbreaker, an electric immunity is often required to force Frosttom to do blizzard. It means one thing, to be on the same level of pressure than frosttom requires two mons, one who counters it and an other with an electry immunity to stop volt switch. It restricts the teambuilding. But there is worse, you understand it stays very risky because almost every electric mmunity is OHKO by Icium-Z. It exists only two mon in zu who have the ability to stop volt switch and counter Rotom-Frost : chinchou and AV seaking. These two mons are normally trash, who the hell will use as special answer a mon like chinchou who has 75 HP/56 SpD as bs and only 36 in def with absolutely none utility move bar heal bell ? Who the hell will use seaking when we have stuff like Relicanth and with AV for I dont know what dark reasons ? Actually they are both used and pretty decent, only thanks to Frosttom. Rotom-Frost makes bad mon legit to use.
On the fence
I can take a lot of time talking about Vigo but I will be quick on this. I think it is broken, very difficult to deal with if you don't have a ghost type or a strong fighting type. Stuff like encore, knock off aren't enough to break it. However, the meta isn't kind with it for the moment so it's difficult to have a good opinion. It needs a good support to avoid to be weaken by hazards or shot down by set-up sweeper. What is certain is it 6-0 unprepared teams and even if you have taking into account vigo in your teambuild, it stays difficult to deal with.
It's unforunately the only replay I've saved where I fight a Vigo. Honnestly, I should have lost in being swept by vigy, only a right anticipation in the right moment saved me. It shows even if you have an answer to vigy (silvally fight here), it's very painthful to deal with if you don't have a really strong wallbreaker or stuff like encore.
Vs pinktidal
Dangerous mons
Its Fire/Blast/Focus blast/Shadow claw LO set doesn't have switch-in except muk and uncommun mareanie and pyumuku SpD. The departure of Clefairy, Altaria and Swanna makes it terrific to handle, especially for offense. Impossible to revenge kill thanks to its gain of speed perpetual and because it doesn't care of three of the five priorities used in ZU, basically sucker punch of pawniard/shiftry and it stops Fake out of Purugly with Protect. If Combusken had 100% of precision on focus blast/fire blast, it would be broken.
I found these two replay very interesting to comment : Combusken vs rains team. A spectator could believe that it's a bad match up to combusken because the half of the team has +2 in speed, resist fire blast and don't have a lot of weakness to focus blast but however, speed boost is very nasty. The first battle I'm outplayed during a big part of the battle but SirCloud does the mistake to kill my grumpig instead of putting again the rain. The second battle is even more expediting because SirCloud didn't have much way to win. If he TW combusken with volbeat, he doesn't have way to put rain anymore and the rest of my team finishes or he sets up rain in hopping combusken misses.
Battle 1
Battle 2
I will be quite rapid here because it's approximately the same that Mushy except it is less broken. The reason why it is only one set is really painthful to deal with, it's its curse set which not really customisable either. Except that, the same story applies here, if you don't have a steel type, you will have a lot of trouble to deal with it, it can 6-0 teams only at the team preview. Since Musharna is better in its role of wincon, muk is played almost only in teams which lack of frosttom switch-in. It stays very dangerous and I would like to see what impact it has in a meta without musharna.
Why I don't think Ursaring is suspect worthy
If for soms Ursaring is a problem for the tier, it's because for them Ursaring invalids the playstyle stall. I specify this aspect because a lot of people think to do not have switch-in is enough to justify a suspect test, it isn't the case. Mawile-Mega doesn't have switch-in, it's not broken anymore. Same with Exploud last gen in RU.
I could say there are way to deal with ursa in stall teams, you have mushy which handle a hit an remove 80% of its life after with its Z-Move, you have dusclops who can take 2 hits without pdr and counter/seismic toss, you can burn stall with protect, tangela can take a hit and leaf storm after that, you can anticipate if it gonna do facade/Crunch with your ghost type. 5 stallers and one offensive mon to RK has always existed like weavile stall last gen in OU or still the amazing combusken stall diagnostic does few months ago, take a pursuit stoutland is enough to trapkill the bear, etc.
But that's not the point. I would like to address an other approach because I think it's far more pertinent than just list things able to bypass Ursaring. If we suspect Ursaring, it's to make stall viable because they are totaly unviable with the presence of bear in the tier. That's the reason why stuff like Mawile-M or Hoopa aren't suspected right now in OU, stall isn't good even without them. Suspect them will make stall better but not make unviable -> shining. In other words, the argument of pro-suspect ursaring can be summerised in two points :
1) Without Ursaring, Stall is a viable playstyle in ZU
2) The only presence of Ursaring in ZU makes the playstyle invalid.
I already disputed the point two above in showing quickly that even with bear in the tier, it's possible to make a stall team valid and there are even few ways to check ursa. You don't have the match up obviously but you can still win. Now, I will show why even without Ursa, stalls have major flaws in the actual meta to be effective. This point is really important because a potential suspect doesn't have sense if not. We dont suspect for theory things but for practise things, if there are other reasons why stall isn't really viable in ZU, a ban is unnecessary.
So why stalls aren't good in ZU even in forgetting Ursa ? Because the meta is simply disgusting with the playstyle. The Z-move are in every team which make SI to simple check, Volturn is predominant and stalls in ZU have no way to deal with it (just run Frosttom + Monferno band/ninjask and you gonna laugh), hazards have never been as easy as before to stack (especially for toxic spikes/spike), we have very good users of koff as shiftry or leafeon who both destroy stall without muk, Stoutland is played pursuit nowadays, Silvally-Dark more common than never, defog users more easy to kill than ever, I would like to see the switch-in in stall to SD MB Pinsir, same with Beheyeem, same with Chatot specs (y there is not only the ursa who 6-0 stalls), taunt are played by various mons very played like grumpig, vigoroth, simipour NP, I don't know how stalls deal with rain (pyuku ?), Mushy Stored power 6-0 stalls without taunt users, the only mon able to switch one time on Machoke guts on stall is Mushy Z-Move/colbur, trick users are in one team on three, stuff like Whishiwashi, Marowak, Servine are painthful to deal with for stall and I don't ever talk about perishtrapper like Politoed or Lapras, stallbreaker like Misdreavus, SD Sub users like Hawsbuck or still the ton of resttalk users who are difficult to be weaken with indirect damages and pp stall some moves, etc.
Stalls are plyable even with Ursaring but gonna stay bad even without Ursaring.
Quick thoughts on the VR
A+ -> A . Already gave my opinion on chatot on the chatbox. I won't repeat but I wanted to point it out.
A -> S . With what I said above, I think I cannot argue more. Mushy is splashable, it supports the team and it is the more terrific thing which exists in ZU. Let it A is a crime, let it join Stoutland and Rotom-Frost on the pantheon of ZU.
A -> Lower .
It was the last time I have seen Rotom-Fan and it was not glorious. You cannot seriously say this mon is as viable as grumpig, muk or combusken in a team. I know usage doesn't mean viability but what is the last time you have deliberality chosen to add R-Fan in a team ? I want to heard the reason with few replays as proof to know why its Pokemon is ranked so high.
B+ -> B . To be a special sponge 2HKO by Rotom-Frost and focus blast users isn't great in ZU. It's not either a Pokemon a lot of used recently. Its curse set is outclassed by all other wincons like muk or mushy. Its classical set isn't great either. Cradily doesn't find its place in an offensive meta dominated by Stoutland, Frosttom and Mushy.
B -> B+ . I didn't understand what it dropped tbh. Sure, SR are more present than before but it accomplishes as good as before its role of tank special. It stays a very good frosttom switch-in and its Z-Gravity set isalways threating and it likes the offensive way the meta is turning now with more mons 2HKO by its Boltbeam coverage.
B+ -> B It's not the best wincon anymore. It has trouble to set up, every team has physical answer and even at +1 it stays slow and be outspeeded by the majority of scarfers. It doesn't appreciate much the shift paradoxally. Once set up, it is as dangerous as before but that's far more difficult to reach this stage.
B -> B+ Very annoying to face tbh. It has flaws of course as it's unability to break bulky mon but otherwise it doesn't really have switch-in. Its Lo/Expert belt Wild Charge/ice Punch/earthquake or cross chop/Flamethrower destroys balanced core, a good speed tier and the opponent doesn't really know what it gonna do. Difficult to use but painthful to deal with.