It's easy with heretic (easier still with experiment with the same electric skill) just know he can shoot or move so kite him on the diagonals shoot and move shoot and move.
Also save your free health refill potion makes this even easier take 2 lightning shots go in close to finish off pop your potion if you get low or swarmed.
Additional strategic advice: if your really struggling look around on the map if your right by a town go see if there's any quests. A easy escort mission or kill some puggles and you will have a level advantage too that should greatly help. (especially useful if your playing with experiment runs and roll a quadriplegic with asthma and thin skill rofl)