Like @Wharflord said a good rainbow team could be: Brienne - Valen - Hawkmoon - Balthazar - Bane
Use +ATK troops over +DEF ones
Pick at least one in that order (regular only):
- (1) The one who buff Attack
- Brienne
- (2) The ones who decrease defense
- Ulmer
- Valen (4)
- (3) The ones who heal
- Belith (5)
- Hawkmoon
- (4) The ones who deal the most damage with fast specials
- Balthazar
- Bane
- Berden
- Nashgar
- (5) The ones who dispel, if needed
- Tyrum
- (6) The ones who increase your defense, if needed
- Kailani
- Gunnar
Bonus - Friar Tuck:
If you need to double/triple greens you could put Friar Tuck near Brienne and Ulmer/Valen and fire his special with to fill their mana faster and have a better +ATK / -DEF uptime.