I first thought repulsion was gonna be great. When you can knock your enemies around to wherever you want, you've got a lot of tactical options, keeping them
away is only one.
Knock their carriers/LRMs into your own shorter-range things.
Push them away from the edge of the gravity well so they can't jump (mind you, if you push them while the phase window thing's already opening, it won't get interrupted - is this intended?).
Push half their fleet away so you only fight a small group at a time, reducing their ability to focus fire.
Scrunch them all up so cleansing brilliance or malice (or both

) can damage more ships.
Move their fleet away from their tactical structures, so you can fight them without repair bays and turrets.
Etc.
In practice though, I found trying to do any of these things almost impossible to pull off due to the point-blank nature of repulsion, and the unwieldy maneuvering of Guardians. Better players than myself might be able to use them to their fullest, but for me, getting my Guardians to all spread around at just the right spots to push in just the right ways seems like way more micro than this game usually needs, and then if they're in a fleet they'll just move straight back anyway.