Wow, that was quick. I beat him in the very first try tonight.
First, I dropped the grass shield and used the crest shield. I also dropped the Xanthous shirt and leggings and replaced them with the black hemmed shirt and my red sorcery dress.
I'm not saying this is optimal, but given my weight, it enabled me to further up my overall magic resistance and stay under 25%.
Second, I used a Magic / Melee approach to the battle instead of Magic only. I was much, much more aggressive with getting in close on his right thigh bone and just hacking at it with my Enchanted Iaito.
Here is how it played out:
1. After exiting the fog, I immediately cast homing crystals and prepared to block the first attack. I blocked the first attack and the crystals fired off and did some good damage as I sprinted towards the dude.
2. I stayed close. Whenever he hovered, I backed a way a little. Whenever he jumped back, I re-cast Homing Crystal and then charged that pocket that's just between the belly and the leg itself. Whenever he did the Wave attack, I raised my shield and took it. The wave attack was the only attack that I felt like I never countered effectively, but I survived.
3. When I got him down to a third, I went combo crazy with my Iaito. That was it.
In retrospect, it was a short battle. I only cast the homing spell twice.
As an aside, I realize now that whenever I have entered a boss battle recently, I have suddenly become a lot more conservative (example: use more magic, stay back more) and I think that hurts my effectiveness. Not only does my play become more one dimensional, but I also don't have a lot of practice with magic only.
New resolution: I am going to dance with the strategy that brought me to that point and only try something different after it clearly fails.
Anyway, I am happy, and I once again appreciate everyone taking the time to offer advice.