Why are you using Resttalk and Flame Orb? With Flame Orb you will no longer be affected by Dark Void and if you Rest, it's free set up time for Darkrai.
Yes, Heracross is still useful in Ubers and it can OHKO Mewtwo with Calm Mind regardless of Calm Minds.
Bare in mind this is a discussion for walls, not Heracross or Darkrai.
<&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