QoH is a goid hero but inferior to BK, so Capt. Nemo would be the red sniper you are missing.
Purple
With so much taunt and riposte heroes you never have enough dispellers. Therefore Domitia.
Green
Sometimes a manna controller saves the day. Thats Zoccs role in a green stack. There are not many green mana controllers despite LotL.
Blue
Frosth shines with other minion spawners to amplify the minions power. He can make a Pengi deadly. Without a bers, Mortega or Pengi he is mediocre. Fenris is situational, Richard with costume bonus fires in 9 tiles with a lvl 17 mana troop . His attack down on three cannsave your team and he dishes out reasonable damage.
Yellow
Norns for Mythic titans, if cou are not interested in MT go Bai yeong for special and heal blockingbor 2nd Devana for dispell. Take xour emblems into account. Dimetimes the second best heto with emblems easily beats the unemblemed best one.