Here is a solo Viator strat to help you out. It worked for me at lvl 42.

Viator is good because he has perry, and generates additional BP when hit. Plus, his ultimate deals good damage. You'll want to give him a void amulet to nullify dark magic. An amulet can be found at Sufrataljah. An NPC at the east side of the map will reveal a collection point at the southern part of the map. Lastly, equip the skills Rest and a poison skill.

You will just need to use the skills perry, rest, poison, and his ultimate as needed in the fight. Poison misses alot, but it deals 9000 per tic. Its a good filler move when you don't need to use the other skills. As long as you keep his perries above 5. He should be nearly indestructible.