I recently completed Violet Hold, having duo-ed it with my wife’s hunter (lvl 54). When the final boss died, my wife got the achievement for completing the dungeon for the first time, as well as meeting the requirement to complete the Assault on Violet Hold: Purple Pain quest. However, for some reason I got neither; no achievement, and the quest is still incomplete. I did die to the final boss, though I don’t see why that should disqualify me.
On another note, why does it say the character I posted this topic with is only lvl 19 when she is in fact lvl 49? Nevermind, it has since updated. Weird that it took that long.