Rollbacks with live service games generally don’t go over well with the players, especially the ones who did nothing wrong in the first place.

The problem with doing a rollback is that, unless you want to spend a lot of time fixing the things the rollback breaks, you have to roll EVERYTHING on the server back. This means all players will have progress reset and items lost. More players are likely to quit the game than Blizzard will lose by banning a few cheaters.