I did a side quest for the Power Draconian, and it turns out that it is impossible to beat. It casts a damage limiting bubble that caps damage at 3000 and then every time you hit it it regenerates back to full health along with its side boss. The side boss also does an insane bolt every round or 2 that does 1-3 thousand health which is a bit high.
The boss has a cheat where if you hit with a rank 6 or 7 (needs confirmation, assuming 6 based on Mount Olympus) and higher spell, they heal. So I had to use Lulu, Ship, and Deer Knight as my attacks.
And yes, it is a very difficult fight that I struggled along with 2 other wizards. I focused on accuracy and used Conviction to avoid the stuns.