Tbh, you can throw him in with empire but usually if it's a team that empire can beat, he just isn't needed and you can just underdog it. If it's going to be a struggle, there are far more useful choices.
There's also the option of putting him under krennic with some random leftovers that you also had to relic. I have a team like that saved if things go wrong. It can take out a c or d team. Or one that is undergeared on defense.
I've used him under ep in geo tb. Though he doesn't add much. But in the first 3 waves you can usually go 4 for 4 anyway. He fills a slot and takes some of the dmg. Unfortunately it depends a lot on rng since it is difficult to get him to taunt unless one of your characters is critical. So far it hasn't saved me.