Personnally I used Kerria+Cherry Sage+Cyrtanthus+Scarlet Tulip+Christmas Rose.
I guess if you replace Cherry Sage by Cherry, Scarlet Tulip by Dalhia/Bride Oncy and Christmas Rose by 6* Alstroe Maria you will get a solid team for Raid Bosses. Just need to keep Cyrtanthus 'cause she give x1.2 skill rate and +30% dmg on RB for whole team. It's insane for a 5* (Scarlet Tulip has only +25% and Cherry Sage +30% for 3 members). Even Sakura has only +35% and she is a 6*.