I've been playing on showdown for a couple generations now, but never really got into monotype while playing. Wasn't until maybe a month ago that I started wetting my feet the tier itself, But it's been a blast so far. The reason I'm leading up with this is as a result, I was unsure as to how good Hoopa-U really was in the monotype tier. In OU as it is, the thing has solidified itself as a monster with an amazing movepool, super strong attack and special attack stats, and the ability to break walls, act as a revenge killer or late game sweeper with choice scarf, or even have a pretty successful run under trick room as well. Not to mention its ability to catch people off guard with it's lesser used but still viable moves like nasty plot, trick, etc. That being said, It is not the only mon that is like that in OU as there are other mons that come to mind right away that i'm seeing people mention here as well cough cough KYUB cough. Not to mention its health and special defense stats allow it to take a hit or two if need be from special attacks. That being said, it does have its weaknesses too, mainly it's typing and defense. While psychic dark are nice offensive STABs to have, it's not the best thing in the world to have against one of the most common moves in the game U-turn, and fairy moves in general. And in this generation, just about every type has some form of physical priority to make its defensive stat look like wet tissue paper.
I got my 2850 yesterday so at this point i'm just waiting for the identification thread now, but this thought process was what went through my mind BEFORE laddering seriously. Honestly, just looking off of OU, despite it being a central part of the metagame, I didn't think it needed to be banned. But as I began to ladder, I read through the posts on here and tried viewing not only my own team, but also my opponents team. If i versed a Hoopa-U I tried to evaluate how much it murked my team or how useless it was against my team. And when I versed a grass team, or an ice team, or a dragon team, I would try to visualize how a Hoopa-U could be built to handle their structure if at all possible.
One concept that is probably completely normal to all of you at this point is the idea of type only bans. I've seen multiple people talk about it in the chat here, and i'm aware that recently (or maybe not recently, i have no clue lol) Aegi was banned on steel only. I didn't understand the concept right away, but after seeing Doublade on steels I began to realize how centralized that mon must have been on that team. I can only imagine how much of a headache that would've been to get around as certain types or even team structures themselves. So after understanding that, I thought that could be a very interesting approach for other mons as well. And after versing a lot of psychic and dark teams on the ladder, I really do think that Hoopa-U should only be banned on psychic teams. I know that's not an option for this, it's either global ban or no ban. But as it is, psychic types have such a variety of mons that they can use, and Hoopa-U only adds to that being one of the most powerful pokemon to that addition. On the other hand, Dark types definitely do gain a lot from having Hoopa-U, yet I never felt overwhelmed by it's presence on those teams. Dark types have mixed attackers to choose from, but I think Hoopa-U is definitely a staple that has made them more viable in the current meta.
All in all, I have no idea where I stand on the matter. I do think that psychic could lose a step or two right now, though I also think both psychic types as a whole and Hoopa-U are not the most out of hand mons in the meta right now. I mean, I used flying and went 33-3 to get reqs with relative ease. If anything, I think some slight balancing for flying would be a step in the right direction, and more importantly I think this involves type bans for that type in particular (but I digress, sigh lol). I think I shall hold off on my opinion for now; I would much rather see what other people have to say on the matter because the choice is difficult for me to make for global or not. I think the type ban is pretty clear cut for me, but i don't know about the one at hand. If I had to make the decision right now, it would be "TO BAN HOOPA-U" just because of how solid it is on psychic with trick room support, type synergy, offensive pressure etc (though I doubt banning it would really change much for psychic considering it's plethora of mons waiting in the back) but i'm still going to keep an eye out on the forums before i make a decision