I have a lvl 20 dervish, only used hench and heroes. I take 2 monk heroes, koss, holy, motivation, fire, and monk hench. You need to make your hero's build as efficient as your own to be effective. Use common sense. You probably do not have the highest armour, go in 2nd or 3rd. Level up faster by doing quests before attempting missions.
My skillbar, from the top of my head..
Faithful Intervention.
Balthazar's **** [PBAOE, fire when it ends, forget name.]
************ [PBAOE, gives energy when it ends.]
Chilling Victory.
Atacker's Insight.
Reaper's sweep.
Pious Assault. Or Strike. Something. [Ends enchant, deals +dmg]
Rebirth/ Rebirth sig.
Use wisely, think aboyut which ench to remove and when.
Lvl 20 Att's.
12 + 1 + 3 Scythe Mastery
12 Mythiscism
3 or 4 Wind Prayers.
Should work like a charm