This fight isn't terribly difficult. He has an Undead > Magic > Undead. You'll want something faster with a dodge to avoid Curse of Doom when it's up, but beyond that you should be okay to have:
*Critter/Aquatic (with critter damage)
*Non-Dragonkin with Dragonkin attacks, preferably a Beast
*Critter/Aquatic (with critter damage).
Here are the links for screenshots on where I found the letter: link and link
At least one of the pets for this strategy require the use of a specific breed.
The strategy offers a TD script that can be used with the TD Script addon. You can copy the script by clicking on the button to the left of the pets.