Toravon = 3 stacks of the debuff on the other tank (Archavon, when he "lunges" for whoever is tanking him, taunt). Same with Gormokk. Same with Lady Deathwhisper. Saurfang = As soon as the other tank gets the debuff. Festergut = Once the other tank gets to 8 or 9 stacks. Putricide = Each stack of the debuff in phase 3 only. That covers all the taunt fights in VOA, TOC and ICC. All else fails, taunt if the tanking tank dies.