Mega Latios is a pretty weak comparison unless you're talking about things that are totally outclassed. As a standalone pokemon Mega Latios is probably like A rank lol but its just so incredibly outclassed by all other forms of regular Latios. Now granted Hoopa-C is kind of outclassed by Hoopa-U, but not entirely. For one thing they aren't nearly exactly the same pokemon (in Lati's case), since Hoopa-C has a different typing which actually makes it a solid Keldeo check (though another Keldeo check weak to pursuit lol) and a spinblocker against defensive Starmie which can't touch it outside of burns. It can also set up Substitutes on Chansey reliably and just in general Ghost is an even better offensive type than Dark just because it literally has 1 resistance and its 1 immunity is rare but still bopped easily (Chansey gets subbed on, Lopunny can't take Psychic STAB whatsoever).
This is not to say that Hoopa-C should not potentially move down - I mean Unbound is certainly a lot better - but it is not outclassed fully in the same way because it actually can play a different role than Hoopa-U whereas Mega Latios isn't doing anything regular Latios couldn't do better, even Dragon Dance.
Just out of interest, where would you put it? I completely forgot defensive starmie existed lol XD I kept forgetting that offensive wasn't its best set (I've been playing BW2 OU on the ladder a lot in the past few days so I've gotten used to seeing offensive on, like, 9/10 starmies). Hoopa-U is a good spinblocker, and it is part of why it pairs so well with Bisharp: they stop hazard removal cold. I think that the Starmie thing kinda clouded my judgement if I'm completely honest. In hindsight, I think either C or C+ (C+ lean) is a better fit for it than C-, so I'm changing my opinion to:
Hoopa-C B- --> C+
So that this isn't a pointless post, I'm gonna talk about a few 'mons.
With Wobbuffet v.s. Gothitelle, I disagree with AM that the two should be on the same rank. I feel that Wobbuffet has the potential to be one subrank higher than Gothitelle due to the fact that it has so much more utility on offense with both its Sitrus and Custap sets than Gothitelle has on any one playstyle with its Scarf set (I would bring up Specs, but that is literal trash). Whether Wobb ends up one sub-rank above Gothitelle or not, Goth needs to drop. I may have a
slight bias as I personally think that Gothitelle is complete trash, but I'm going to try and set my bias aside for this. Wobbuffet's access to moves such as Encore, Destiny Bond, Tickle and Safeguard in conjunction give it lots of utility before consideration of Countercoat and Shadow Tag. As a trapper, Wobbuffet is great utility to offense due to its ability to come in and shut down the key threats to your team. However, this is not something Gothitelle can do. In my personal experience, I have the most success using Gothitelle on semi-stall and balance. This is because it traps and removes select threats to said playstyles with coverage options like Energy Ball/Thunderbolt and HP Fire, and said teams benefit much more from the offensive presence than from Wobbuffet's utility options. However, in its current state, the metagame is more friendly to Wobbuffet, who not only thrives on offense, but also against it - where it can deal a lot of damage with the combination of CounterCoat and Destiny Bond, as well as turn setup 'mons into setup fodder with (possibly Custap) Encore or providing free turns to its teammates v.s. tanks by using Tickle a few times and turning them into setup fodder for one of Wobbuffet's teammates. Its disappointing that it can't carry all of CounterCoat, Encore, Destiny Bond, Tickle and Safeguard on one moveset, but really your choice between Destiny Bond, Tickle and Safeguard is about as influential as your choice between Dark Pulse, Grass Knot and Hidden Power Fire was on Greninja: it comes down to the teams needs (D-Bond if offense is an issue, Tickle if balance is an issue, Safeguard if stall is an issue), meaning it doesn't have any major effect on Wobb's effectiveness. The main problem with Gothitelle compared to Wobbuffet is that it doesn't really have the options to take on offense (the dominant set of playstyles atm) that Wobbuffet does once its tricked its scarf to something, and that is huge when you realise that, while it dumps on certain teams, it falls flat v.s. the dominant playstyle - leaving you in a position where you effectively have 5-and-a-bit pokemon in certain matchups. As Of Moose & Men said, Wobbuffet is almost guaranteed to have utility in the vast majority of matches it is in (provided that someone with a brain is using it) due to the sheer utility of its status moves in conjunction with Shadow Tag and the sheer power of countercoat. This is most certainly not a trait of Gothitelle, and that is why it should be below Wobbuffet. While it is debatable as to whether Wobb should move up (I personally think its consistent enough to warrant B-), Gothitelle should definitely move down. Therefore, I'm going to say:
Wobbuffet C+ --> B-
Gothitelle B --> C+
Speaking of Trappers, I agree with AM on Dugtrio. Its not very hard to pair it with teammates which can lure Heatran and pop its potential balloon (namely U-Turn Scizor), but with Heatran being on so many teams nowadays simply because it is so freaking versatile, the ability to reliably trap and kill it is huge. Dugtrio needs some support to function (namely VoltTurn support to get it in safely), it is certainly consistent and self-sufficient enough to rise. All in all, I feel it is about as consistent as Wobbuffet with a smaller pool of what are overall a more notable set of specific traps that it can fulfil consistently (Heatran, Magnets, Scarftar etc.). This, I feel, puts the two on the same level. Kinda thematic, but this thing is another great partner for Hoopa-C due to its ability to reliably trap Tyranitar - one of the premier pursuit trappers. Therefore:
Dugtrio C --> B-