Ok, I have a partial answer for this.
I had a look around, and it turns out ALL Peacebringer self heals, and the Warshade Dwarf Self Heal (but not the human form Warshade self heals) are ALREADY unresistable, on Live. I have no idea what their healing resistance caps are, but it does answer why they aren't in the changes.
EDIT: Same with the only Arachnos self heal, Serum, already unresistable on Live.