I can confirm (
) that Wizardslayers spell failure on melee hit works on all incarnations of Jon Irenicus in Tactics Mod in SOA.
So - if you want to make fun of him ...
My WS/T was dualled at level 10. He wore Human Flesh Armor, Cloak of Balduran and Carsomyr and had all together 105% MR.
(he was mage's worst nightmare)