I personally can't go without Awareness, it might be dumb but I get really salty when the boss crits, and will use awareness in response.

However, I'll always take Shirk into an 8-man, because it's a really good skill. Were tankswaps going well before 4.0? Yes, they were. But there were always those times, like when a tank use provoke too early, and ends up an entire Berserk - Butcher's Block behind you in enmity.

Really, I just exchange Shirk for Low Blow.