Wands (both to enable them to last when some of their spells fail, and to, for example, wither the polearm out of the guy's hands). Remember you only need to land one grease to swing things a bit.
Shield of electricity, if they are using metal weapons.

Overall though, a wanded up voker can normally blast the warrior into fleeing. Also, spell selection would change. For example, that acid stream spell becomes arguably a better choice.