First and foremost, I'd like to comment on hazards (spikes, specifically) as they have been a major facet of discussion in this thread.
I feel like Spikes have became a vital part of pretty much every BW2 metagame (moreso than they were beforehand). Having played BW2 OU, UU, RU, and NU in the recent series of PLs and in other tournaments, I can say that Spikes seem even more important to have on or to rid from the field than ever as of late. I have two theories as to why this is: 1) the fact that generation six's Defog mechanics have made it harder to keep hazards up and thus when temporarily transitioning back to generation five, spikes' effect is emphasized (specifically when teambuilding) and/or 2) it is just a "coincidence" of sorts given various metagame trends making spikes increasingly effective. I feel like the former of the two aforementioned theories is more realistic and credible as past generations' metagames being effected after new generations are implemented as a byproduct of significant new generation changes from previous norms is a common occurrence while it would be an unlikely 'coincidence' for this to happen as it's not only BW2 OU being more spikes happy as of late, but other BW2 tiers (
especially NU , given the lack of spinners) have also been subject to this.
As for the prospect of this surge in Spikes' viability and effectiveness being potentially dealt with through a limitation or ban of this move, I am on the fence. Before I even consider if any tiering action is warranted or not given the effect of spikes on BW2 tiers, a red flag comes up in regards to how dealing with spikes would potentially set an arbitrary precedent of sorts. By this I mean that banning a move as a whole, which may not be necessary in this case despite it being a potential solution to the problem, is generally avoided in favor of banning a pokemon. If we were to ban spikes, it could easily lead to people advocating bans of other moves instead of the traditional approach of banning a pokemon (for example, banning V Create instead of Victini in UU could be argued when given our tiering system's history, banning Victini as a whole would be the proper line of action if it was deemed broken). This may be a bit of a slippery slope, but banning something like spikes would be hard to justify without provoking situations like the aforementioned regardless. If we were to do something like try to limit spikes to one layer (not advocating this, but somebody mentioned this in either this thread, an RoA thread, or a WCoP thread - cannot quite remember which or who), this would directly contradict the actual in game mechanics, which is a whole other can of worms that I think we should try our best to avoid as then, people could easily start to propose all sorts of manipulation a of game mechanics in order to fit the various metagames better than actual mechanics do. Furthermore, I am skeptical to even propose or advocate any tiering action on Spikes. With that being said, if this were to be overlooked, I would be in favor of a suspect of spikes in some way, shape, or form to at least test the waters with the potential end result of improving either the quality of BW2 tiers if spikes were deemed banworthy or deeming that spikes aren't broken and at least being content that they were given a suspect to test the brokenness.
Now I will transition into discussing Reuniclus, as an individual pokemon in the BW2 metagame, and if it is broken or not, in my opinion.
Reuniclus has two sets, both of which have their merits, but the bulky Calm Mind set warrants more attention when discussing if it is broken or not because while the Offensive Trick Toom variant can be potent (especially against offense), it is much easier to check (or "play around" given that TR puts it on a timer) and not as much of a threat to sweep any unprepared or underprepared team.
The following are what I deem to be fair checks or counters to standard CM Reuni (Psyshock, Focus Blast, Recover, and Calm Mind with HP and Defense invested in heavily) with the conditions for them to check Reuniclus in parenthesis immediately proceeding their mention: Jirachi (Wish CM, Trick Scarf, and Flinches - especially with paralysis from Body Slam, Thunder, or team support), Tyranitar (Chople with 88 attack EVs Adamant - or more - and Crunch or CB - switching in at the right time although it can probably live a +0 Focus from full or maybe after SR if it doesn't run too much speed instead of HP, but cannot calc because on phone and not too solid a check given that it is still a 50/50 with Crunch/Pursuit as Pursuit doesn't always 2HKO if it stays in), Scizor (Band, Roost SD, or offensive SD with a bug move; fun fact: scarf uturn does around half - maybe a bit more - to 252/252+ Reuniclus and when using Scarf Scizor as a check to Reuni late game, I have lost to it quite a few times as it Recovered after U-turn and CMd on other things while I couldn't switch around and back many times given hazards and focus blast damage on Scizor), Sableye (immune to both Psychic and Fighting types, carries taunt, and can damage progressively with Foul Play or Night Shade, so this is the hard counter to CM Reuniclus), Taunt users with Recovery and come in before Reuniclus boosts to the point where it can threaten the pokemon with Taunt+Recovery (Stallbreaker Mew, aforementioned Sableye, Jellicent, uncommon Taunt Gliscor although it has to be super careful here, etc.), Overpowering pokemon that don't take too much damage from Reuniclus (CB Dnite if it doesn't get recover stalled out + confused early because it's doing around 70, Dark Pulse Hydreigon - not a lure or a reliable check but Jirachee used this vs me recently and upon discussing it with him a bit after we played. we came up with a spread for 'new' meta Hydreigon which outpaces all non-Scarf Excadrill and uses the EVs that are leftover after speed investment and Timid nature to tank Focus Blast from +0 Reuni after SR and some other condition I cannot quite recall - either sand or LO - it was like 56 hp 20 SDef or something and I can dig up specifics when I get on home and check IRC logs later if I must, CB Metagross which I know Leftiez has messed around with a lot recently despite it not being common otherwise, the uncommon but godly CB Garchomp, aforementioned CB Tar, and various other things), and pokemon who can use Reuniclus' admittedly passive nature prior to being boosted to set up a counter-sweep against it (QD Volcarona can tank a +1 or maybe even +2 Psyshock depending on if Reuni is LO - which people like Peachy are using recently to win Reuni wars and do more damage - or not and how much HP investment Volc has while QDing or Bug Buzzing, aforementioned SD Scizor and Wish CM Jirachi, CM Roar Latias like the one SW used vs Lavos in BW Cup Semis, NP DarkPulse/ShadowBall Mew like the one SW used vs Jirachee in SPL despite it being very uncommon, etc.), and various miscellaneous things like putting it to sleep or encoring it being temporary answers to this permanent problem.
As you can see, there are a fair amount of checks/counters and means of getting around a CM Reunuclus sweep, especially if your team isn't too passive. I would argue that things like Volcarona, Kyurem-B, and some others have less checks than Reuniclus. HOWEVER, these pokemon lack a couple noteworthy merits which Reuniclus possesses such as Magic Gaurd, superb natural bulk, and having many opportunities to set up or free turns in general upon switching in. Given the above, counterplaying Reuniclus when using a standard bulky build (let's say something like Hippo + scarf tar + spikes from Ferro or Skarm + probably a Jellicent + bulky filler + something to get the team somewhere that could even be a Magic Gaurd Psychic itself or really any of the other various variants of bulky offense / semi-stall which people use often) very challenging if not impossible when a team is completely unprepared for it.
Now this is where I sort of come to an internal dispute over Reuniclus. One part of me wants to be pro-ban because it does consistently well against this developed standard widespread archetype and some other teams while the other part of me wants to say that people should actually prepare for Reuniclus like they would another prominent threat, like Keldeo, and bring at least one if not multiple stops to it regardless of the team/archetype. After thinking this through a bit more, reading this thread, and seeing things like the puush Ciele posted with Reuniclus' results in major BW2 tournament games recently, I am leaning towards the latter (people should adapt more to Reuniclus and having ways to beat it on all teams). I still wouldn't be opposed to a suspect at some point down the line, but I don't think it's immediately necessary, nor as urgent as some other posters say it is (everyone is entitled to their own opinion, of course, not saying that they are wrong or I am right, just stating my own opinion).
TL;DR: On the fence about Spikes but question the terms on which we could even suspect/ban it without straying from tiering policy and precedents. Leaning anti-ban on Reuniclus, but I don't feel too strongly and can be persuaded otherwise.
Sorry for any mistakes or typos as I'm typing this on my phone. Also, idk how much weight will be given to my opinion as I've only been a part of this subforum for like 18 hours, but I play BW2 a ton and have a lot of interest in the tier, so felt the need to leave my two cents.