I've got a way to "legitimize" this solution in terms of roleplaying for those who might think it's a little cheezy.

First cast Chaotic Commands on yourself to protect yourself from their psionic blasts (and the umber hulks' confusion gaze). Then have a supply of potions of genius handy (to give yourself a buffer from their psychic drain). Then cast your blade barrier and have at it.
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[This message has been edited by Memnoch (edited 06-11-2001).]