First suggestion: more lvl 60 champs. Second suggestion: you definetly need Vrask, he is the only healer among your Orcs, mvp in this faction (I don't have him and can't beat the last boss at stage 21).
Brago, Seer (to remove enemy buffs in waves with Valkyrie or stuff like that), Zargala (decrease def), Sandlashed, Vrask.
A lvl 60 Vrask & Shaman with reasonable gear can get you to Stage 20.
In fact, Vrask & Shaman together can make your Orc team Unkillable because Vrask will do constant heals & Shaman will do constant revives and both of them together can you your team live.
The issue you will have is "Damage".
You need some burst Damage which means you will most likely need Kreela.
First suggestion: more lvl 60 champs. Second suggestion: you definetly need Vrask, he is the only healer among your Orcs, mvp in this faction (I don't have him and can't beat the last boss at stage 21).
Brago, Seer (to remove enemy buffs in waves with Valkyrie or stuff like that), Zargala (decrease def), Sandlashed, Vrask.
I like Skadi's suggestion of Brago, Seer, Zargala, Sandlashed and Vrask. All excellent champs that should be able to, especially at 60, take you through 21 without a crazy amount of trouble.