This is not the result of a bugged ability. From what I have observed, every PoP solo named has a stupid mechanic which first appeared on certain Kunark Ascending heroic named (e.g. virtually every named in Arcana’se Spire: Forgotten Sanctum) which makes it immune to damage at specific thresholds. Apparently, they do not want overgeared players killing these named any quicker than 20-25 seconds. As a result, the stats on your gear beyond a certain point becomes little more than cosmetic fluff. Sounds fun, right? :roll eyes:
Welcome to Everquest 2: Planes of Guild Wars.