Oricorio has the new Dancer Ability that no other Pokémon has had before. If another Pokémon in the field uses a dancing move, then Oricorio will be able to use the same move immediately afterward, thanks to its Dancer Ability.
Sounds situational until you think about double/triple/Royale battles. You could build a team of Oricorio for double/triple battles that just use dancing moves over and over to get free buffs and attacks in. I hope they can learn Baton Pass.
As someone who plays triple battles almost to the point of exclusivity I'm not too worried about it. First off we don't know too much about how exactly it works.
* Does it replace your preselected move? (probably not)
* Is it limited to one use per turn? (probably not)
* Does taunt prevent the copied move from activating? (probably)
* Does the activation have a unlimited range in triples? (as in will it be able to copy a dance from a left side pokemon when it's on the right? and, probably)
* Is the pokemon actually bulky enough to survive a round of triples when your opponent knows exactly what yer doing without a first turn protect? (hell no)
* Does it have decent moves to make use of the stat boosts or at least baton pass? (Who knows)
And second when people do bring pokes that are pretty much just one trick ponies to triples they tend to get countered hard.
I don't think I've lost a fight in cartridge triples because of something using Dark Void in ages. It's a similar thing to exploder electrodes, sturdy shedinjas, and beat up terrakion. It becomes incredibly obvious what you are doing and once people have lost to it once or twice they'll make a modification to their team (often slight) that shuts your plan down in one, maybe 2 moves.
In this case, a quick feint to break the obvious turn one protect then probably any reasonably damaging move, and yer opponent is one poke down, your opponent has probably spent their first turn buffing (which while not useless, is less impactful than in singles), and you still have one poke free to lay in some hurt to the rest of the team. And that's just what I came up with in a minute or so. It could probably be countered more efficiently.