Player A pulls mob with proximity aggro only, no damage items in both hands. Not casting on mob or self, not doing anything. Player B also has no damage items in both hands, is also not casting on mob. Player B taunts. Receives successful taunt message. Mob does not change targets. Additional taunts from B do not cause the mob to change targets and return the "You already have your target's attention" message. Player B spam buffs player player A (resist cold in this test) mob still does not change targets. Player B directly interacts with the mob with a debuff - aggro immediately transfers to B. Player A now taunts with the same results as B above. Player A spam heals and buffs himself, no target change. Player A spam heals and buffs B, no target change. Player C spam heals player B for several minutes Player B still on target being attacked. Player A's taunt message still returning "You already have your target's attention" message. B feigns, mob immediately aggros C. Anecdotal conclusion: Mob target is not updating until the person on the top of the threat list directly interacts with the mob. Any player-to-player aggro creation is being ignored until that moment.