Pretty decent champs overall. Here's my stab:

Skullcrusher (counter-attack, ally protect) - try to give him as little accuracy as possible

Frozen Banshee (poison, poison sensitivity)

Tayrel (def down, atk down)

[DEF up champ] - find someone with a 2-turn DEF up that has a 3-turn cooldown

[block debuffs/cleanse debuffs champ] - find someone with either of those. worst case scenario you can run Minaya on a 4:3 rotation

Tayrel is your next champ to 6star for sure

You've invested in Aothar already, wisely or not.  While FB is better, especially with CA from skullcrusher, I am not sure if I would worry about another CB only champ at this point.

I would work on getting to dragon 20.  Zelotah or Rector might be next choice after Tayrel.