Has Trick Room Nasty Plot Cofagrigus always been this good? I'm struggling to find any good checks to it. One thing that comes to mind is Sharpedo; it's fast with STAB Crunch. However, Trick Room renders that useless. In addition, Cofagrigus is bulky as hell, so it can take anything and retaliate. Another thing that comes to mind is Mandibuzz, which I never see at all. In theory, it can use Taunt to stop it from setting up, Toxic it to give it a time limit, and phaze it with Whirlwind. However, using Whirlwind leaves you Taunt bait.
Cofagrigus gets perfect coverage with just two moves. Normal-type special walls like Clefable and Munchlax eventually stop liking to take +6 HP Fightings. The fact that it's best counter is stopped by many of the top special attackers in the tier (Lilligant, Manectric, Omastar, Rotom) is really no help to it. Slowking is a better choice than Mandibuzz in nearly every situation for its superior defensive typing, better attacking options, and Regenerator.
Is Spiritomb even a counter to it? I don't think so. Sucker Punch is Spiritomb's strongest move against Cofagrigus. Never mind the fact that Cofagrigus outspeeds under Trick Room.
252 Atk Adamant Choice Band Spiritomb Sucker Punch vs. 252/0 Cofagrigus= 78.222814%-92.026841%
The Calm Mind set doesn't do anything to Cofagrigus either. Spiritomb will never OHKO at +1, and isn't even guaranteed to at +2.
0 Sp. Atk +1 Bold Spiritomb Dark Pulse vs. 252/4 Cofagrigus= 73.138284%-86.045041%
However, Spiritomb can't switch in at all, even with Trick Room up. It is a guaranteed OHKO after Stealth Rock and 2 layers of Spikes.
252 Sp. Atk +2 Quiet Cofagrigus Shadow Ball vs. 252/4 Spiritomb= 71.466442%-84.078167%
As you can see, Cofagrigus is definitely a force to be reckoned with, and I think it should at least be put up for suspect and voted on by the next RU Council.