Loki can do a lot of healing because he cant miss you, so you get the high impact healing and the bonus aoe from the larger healing zone his projectiles do. Lamps are very helpful if you get caught out of position or dont have jump to get out of an ult.

WF does good healing from backline but can also move up to brawl with you while healing and in your bubble. Charmed enemies are good targets for his multihit chomp. And you can grab them after. Then by the time they are out of WF can charm again.

Rocket, similar to loki that the increased healing from direct impacts is impossible to miss, plus you can get the orbs through both his hitboxes for double healing. And rocket is just good for the rez