Yesterday I did Ex Roulette, and before greetings were muttered the tank (WAR) took off and pulled the first 2 mobs (AK-HM) and engaged the doorkeeper. I Regen'd the tank, Medica 2'd, then spammed holy 2-3 times and the fight was over - easy, no problem, no hard feelings.
As soon as the door was open he ran thru the two wolves, Big-Horned thingie, and AOE vines that slap the ground and beyond. He only used proximity (as opposed to Flash/Overpower/Tomahawk etc.) to aggro the mobs. Unfortunately he still had some regen active from the first fight. A wipe followed shortly thereafter. Derp, right? But whos derp is it?
He blamed me; "Don't use regen."
I blamed him; "You might try slowing down and Overpower."
I'll leave it to the jury of the community. Is aggro management from status effects (Regen, Medica II, Bard songs, Pet Casts, etc.):
A) the responsibility of the caster.
B) the responsibility of the person who "pulled" the mob.