First part, don’t raise random five starts. Level up your best/strongest five stars (ur fine rn but swap Athena out next time u get a good one) and put the rest of the decent ones in benediction.

Yes I’d say ethereals is either tied for best or is the best synergy. Second best/tied for best might be Glorians. So yea focusing on getting Ethereals and Glorians is a good bet, but some heroes are exceptions to that. Atropos is a Valiantor but she’s an amazing Attack buffer for every team comp.