I think the biggest problem right now is Memento Rain Dance into ShellSmash suicide leading, and the fact that there isn't really anything in the tier that can handle it. Quagsire gets murdered by HP Grass, Swoobat still can't overcome Gorebyss's double speed from rain, Trace Gardevoir can't outspeed because of the shell smash boost unless it runs with a scarf, and Absol can't reliably kill with sucker punch because the game devolves into a massive guessing game of "Shell smash or attack?" It's like Russian roulette, only if you lose a giant killer pink fish kills you and your friends. And even though you can burn all 7 turns of rain in a worst case scenario, you're still dealing with a +6 extremely pissed off giant killer fish. On this plus side, this leaves it highly open to propriety, but on the downside, if you have no priority aside from Absol you are utterly screwed.
Honestly I think that, instead of banning Damp Rock, we should ban the primary offender - Gorebyss. Gorebyss in the rain is simply too overpowering for the tier, especially with a suicide memento dance lead, since those -2 stages mean that you can't even kill it before it gets a smash up. I am going to keep testing it, as I am not a particularly high ranked player, but I think at this point we would be better off just banning Gorebyss, as damp rock and the associated mons in and of themselves are not broken, as Trace Gardevoir still exists to handle them (Run signal beam over shadow ball/focus miss!). The problem is that the only thing that can counter Shell Smash Gorebyss in the rain is Choice Scarf Trace Gardevoir. It's not even difficult to get a Shell Smash in the rain, as memento's -2 makes the damn thing nearly impossible to kill given the power levels in NU.
And since the only counter is one, choiced pokemon, it is beyond simple for your opponent to just swap into something with, say, volt absorb, or grass and electric resists, as they know you will be using either Thunderbolt or Energy Ball (and who uses energy ball on Gardevoir nowadays?). Technically, Ludicolo serves as a check, but it gets 2hko'd by HP grass 100% of the time, even if gorebyss gets low rolls, unless you're running Tankicolo. In that case it only gets 2hko'd some of the time, a small comfort. God forbid it takes a high BP neutral attack (ice beam) instead of sub, in which case it will always 2hko.
Math here on Gorebyss's speed in the rain post shell smash, btw:
52 * 2(swift swim) * 2(shell smash) = 208
Gardevoir W/ Scarf post swift swim trace
80 * 2(swift swim) * 1.5(scarf) = 240
Gardevoir w/o scarf
80 * 2(swift swim) = 160
tl;dr ban gorebyss