Didn't know that about the skulls. I was always wondering what that effect was when they hit you, but was always too focused on the fight to really pay attention to it. I have been slowing things down with him lately, though, and having decent success. My health and lives usually dictate my mindset, as I usually do pretty decent when I limp into him and don't expect the fight to go that long, as opposed to being at maximum health and lives, and I get reckless.
I think it's just me. He's a bit of a damage sponge, and I just get impatient trying to wipe him out. He is a great final boss, though. I'd probably get bored with the game a lot faster, if I was just walking through him all the time. Shit always gets real when you hit that final zone.