Is the Bad Batch a good team?

I wouldn't say they're top tier, but they are very good. There are probably other directions that would serve you better though. I would look at a new players farming guide to get a sense of what teams are the most efficient in early game. You'll want to make a plan for how you want your roster to progress so that you don't waste resources. While BB holds up well, they're very expensive in terms of gear - that same gear might give you better progression if it went elsewhere.

I'm at 8.5m GP and I don't have any of them above gear 9 - they'll stay there until I'm ready to pursue Lord Vader. They still punch up quite well though, and I still get use out of them even at that level.