Boss Level: -X% avoidance or -Y defense?
I've posted a question on the official forums about this, which you can find here, but I'm linking it here for our US numbercrunching friends as well.
I have yet to find any WotLK evidence of either case, so I'm currently clueless as to which way it should be. 415 baseline defense sounds the most logical (easier to program & can be ported to PvP with e.g. 399 defense skills etc.), but I can niether prove that theory, as I can disprove the current 0.6% theory.
Any thoughts/suggestions/help? :)