The in-game ratings can be a good first clue if a champ is decent (as long as it has a lot of ratings, say 1k+)

If a rare is over 4.8+ in an area I'd look it up (Hell Hades site) and look at their skills closely.https://tutuapp.uno/ 

reddit spambot alert.

@ClosedPoly  the list that Moored posted is pretty good. That said, you probably should look at it more in terms of "what do I specifically need for objective X", since you're far enough advanced in the game to not need to use most of them.

So you're that guy with a 4 Coldheart Arena Defense team lol

Lol, nope. Built the 2 50s awhile back for the dark elf-only spider tourney.

I'm pretty sure I've cleared every DT rare-only secret room with these guys

I've havent yet cleared Sin City Hard, but I'm very close. I can't recall if there are any stages left I've never beaten where I'd use a rare, but I doubt it.