I think one main advantage I have over you (despite it not being that useful for Crawmy) are my talents that increase my shield capacity and max health.
Right now I have about ~4170 shield capacity and 2777 health.
I feel like he attacks for a percentage, rather than a preset figure.
Yes he does. I have about 3200 shield and ~1200 health, and he still doesn't oneshot me. A single melee hit brings me down to ~5-10% health.