Which healer would you recommend?

[Cynfael]

SCH is really good, but it's going to require more effort to learn to play well. It's less forgiving than AST/WHM. If you're just looking to switch for a bit, AST is a good call.

I'd say that the opposite is true: SCH is very forgiving to pick up and run with, albeit with a lot of potential at the skill ceiling.

WHM and AST have a more straightforward healing style without pet management, but it's the pet that can help carry mediocre SCHs where WHMs and ASTs on a similar skill level might fail.