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.

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.