For the assumed MP issues you just need to stack a little more PIE than on others gears because it's complementary to SS. Then, if you're good enough, you won't have MP issues. I always hear the same problem with the PT for the dps but actually if you're good enough you can pass through this constraint. Just need to practice and adapt.

And healing faster means fulling up the target's HP faster, so you would need less Swifcast or Benediction to save your target, cause you'll always be healing faster your target and preventing her from getting into a tense/critical situation much more.

But ofc, you need a lot of SS to see the effects of it, I won't say the contrary and it's the same for the others stat anyway.