Just scrap Substitute off from Psycho Killer. Mewtwo can just smash Ferrothorn with Fire Blast regardless of weather. There's no way Ferrothorn can wall Mewtwo.
I actually agree with firecape on the Ice Beam slashes. Ice Beam is really important because it hits Giratina and Lugia harder than any other move. It's your only way to 2HKO Giratina directly(after SR for better chances) without any boosts and destroy Lugia at least some of the time. Getting walled by Lugia outside of sun isn't fun at all.
Aura Sphere smashes Tyranitar, Heatran and Dialga. However, Fire Blast already smacks Dialga hard in the sun, even +1 Ice Beam 2HKOes it. Heatran is rare and Tyranitar is not overly common. Ice Beam also knocks out Ground Arceus/Grass Arceus easily. Psytrike destroys Kyurem already and Fire Blast hits Steel Arceus harder.
StallTwo is still fine when I used it. If you are mentioning Victini, you might as well mention Cresselia too. Without Fire Blast, Cresselia can come in and paralyze/toxic you, set up Light Screen, Moonlight off the damage and do nothing else.
Agreeing with barry. Bulky Mewtwo is a waste of its sweeping potential. Without much Special Attack EVs and Calm Mind, Mewtwo is pretty weak. Even physically defensive Ho-Oh walls you.
firecape is strong and I trust him more than anyone here :)
QC APPROVED 1/3
<&GreatSage> if nothing else it's a "trickroom teaches pokemon" thread
<&GreatSage> which is reason enough to keep it
<@Colonel_M> I once heard Jibaku considered Scarf Gyarados for his Ubers team
<syrim> Trickroom the ultimate synguuest