FWIW I think the team I beat Fang Moor with (needing eleven potions of power) was 3x Dargon and a Shaman of Set. It seemed better to create red gems than skulls, and Horned Viper did, as you mentioned, too little damage to be reliable.
Edit: based on my own Fang Moor rant post, it sounds like I used 2x Dargon, a Setauri, and a Shaman.