I used Tahlkora (level 20 set to pro/heal), Dunkoro (level 20 set to pro/heal), Acolyte Jin (level 20 set as B/P w/level 16 Wolf) , Menhlo, Lina, Cynn, and Eve. And myself, level 20 WaRan w/pet (level 16 lioness).
I was amazed how it all worked so well, with planting flags etc. I think having pets really helped as they kept things busy while we fought. Sure they died a lot but it really seemed to help somehow.
Man, Heroes rawk! (with 4 monks it's way easier

Here is a screenshot of the heroes settings. (In case anyone wants ideas for theirs).