I went for the doctor at level 20 and stuggled too but also really enjoyed the fight, one of the more fun one.
The demon are a massive pain in the ass. The doctor though, is rather weak UNLESS he can steal your source in which case, get ready for some good old "Epidemic of Fire" and BOOM! Also, if you trade with him first, he will gain access to all the items and use them in the fight. This is both bad and good.
The bad, he can use all those magic scrolls and potions.
The good, because he's using them, he is wasting AP on them instead of beating your face.
You can just trade with him and buy all the good potions and scrolls so he won't get to use them while also gaining access to them yourself. Leave the useless potion you don't mind on him and it can save you a few turns of damage.
You can just cheat and kill him before he change his form which really kill the fight and make it way less enjoyable. Just save scum until Arrow storm crit enough and use a knock down arrow on him. Not really recommended.
What you can do to fight him normally though is to have the ranger use Arrow storm along with source vampirism and source orb. This way, you are able to use Arrow storm twice in the fight to help with clearing the adds.
And instead of flat out killing the enemies, sometime it's best to just keep the early turn enemies CC'd especially the faster one that go first and focus on killing the slower adds instead just to minimize the damage.
And as mentioned on the first paragraph, never let your magic shield break or you're in for a world of pain after he steals your source point with his source vampirism. With someone having maxed Leadership (for the resist+dodge aura) and keeping Evasive aura up for at least 2 turns, you shouldn't suffer much damage outside some spells here and there that should be easy to recover with Dome + Soothing + Mend armor. As long as your magic shield doesn't reach 0 before the doctor acts, you should be able to do this easily and evne if he does get Epidemic of flame out, if your fire resist are high enough, you shouldn't die. If you have some slotted armor, put the fire one in there now for more resist.
And if your team has a lot of magic damage, charm arrow becomes really good btw.
Last edited by Ellezard; 23/09/17 08:22 PM.