On the Wrynn leggings, I have 'em in the bank. I was using T4 while I was hurting for +Def and never switched back. I'll do so tonight.
We generally have a warlock on CoW for any boss that hits moderately hard, but 2/5 imp demo could free that up. While we generally don't have dps problems, more wouldn't hurt anything.
Lastly, on the +hit gem, is there a standard stamina to hit trade off? In this case it would be 9 stam for 8 hit, so about 13 hp to one hit rating with vitality and kings taken into account. Without the set bonus, it'd be a touch over 17 hp to one hit.