1) balance between aggro generation and survivability is like balance for accuracy and offensive stats for melees and mages, nothing new here. If anything, defence it's a useless stat like is working now on bosses and highter level mobs. If you feel it wrong, ask to be reworked instead touching enmity+/-

2)And the problem is ? In every game with pve/pvp, people have 2 different sets with gear focused on pvp, what's the problem ?

3)look first answer. And actually in the long run, a proper tank never allow a dd to surpass it. You're looking to mistress, where dd go in full attack immediatly, or a soo-soo war