Your roster is totally ok for free2play.

Elhain and Mordecai are good champs for their purposes, but not for CB. Elhain has two moves that can attack all enemies, she is great to clear campaign stages or dungeon waves 1 and 2. But in CB, there is only one enemy, attacking "all enemies" doesn't really help here. Beside her raw damage, she has nothing to offer. Good champ in general, let her run campaign to lvl up champs for the tavern, and use her in dungeon teams, but nor for CB. Similar for Mordecai, he is the Spider killer, but CB is immune to turnmeter reduction. All he provides vs. CB is one burn debuff. That's not good enough to be in the team.

For now, I would go with Ronda, Uugo, Dhukk, Gravechill and Mausoleum Mage. Gravechill only because she allready is lvl 60. Wihthout her friend, the Frozen Banshee, who provides poison sensitivity, Gravechill is not really good.

Mausoleum Mage would be my next lvl 60 with that roster anyway. Exept Uugo, all champs lvl 60 so far are for offense. Mausoleum Mage would fit quite well, he can help your team to stay alive in CB and Dragon 20.

Very interesting roster, I'm excited to see what the experts can come up with. 

I wonder if you could use Marked maybe instead of Mordecai and Ronda instead of Elhain for better results.