I dunno about healer. I've only been on my tank so far.
But most of them are not necessary.

If you ever need provoke or the AoE provoke it's because you don't know how to tank. Shirk is likely the same.
Needed: low blow. And maybe 2-3 damage mitigation abilities. That leaves 1-2 options beyond that that are filled by... well... there's nothing vital left.