I like the concept. There's something funny about the fact that I had a run where I deflected bullets into random directions and that mistake stayed with me until the end. The parry seemed very forgiving tho, especially after upgrading it a bit.
I've gotta say, I didn't even get to see much of the last phases, I think his health drops extremely fast at the end there - with all those upgrades and runs. But it did feel good :)