Changing equipment so that you're more ideal what-nots for casting different spells would go a long way towards killing the-dude-whose-name-I-can-not-recall before he kills you. This would help your Vorpal Blade damage as well.

The AF hands, in particular, are doing nothing for you at all other than filling up a slot. Even with the limited options that come with being level 70, I'm sure there's lots of stuff better than AF hands or feet.

Zephyr Mantle provides one more shadow than the Blink Band and Sprout Smack will (probably) slow him, if you're beyond desperate.

You might consider changing your food to pizza for more accuracy, although I have no idea what the-dude-whose-name-I-can-not-recall's evasion is like.

Other than that and the points Raefien and Kwate already made, just keep at it. He has a huge pool of spells to choose from, so there's always an element of chance present.