According to
Torven’s research on mob avoidance and mitigation, common NPCs cap out at about 200 mitigation from level 50, whereas the harder velious boss mobs have significant ac (we’re talking AoW 900, Vulak 1000). I make the assumption p99 echos these findings, if not matches them perfectly.
While your parse against the giants is very useful to do a comparison for weapons against xp mobs (and according to Torven should be applicable for xp mobs all the way to 60 thanks to that mitigation cap of 200), I don’t believe it has much generalisability for the harder bosses, which seems to be a focus of the current tangent of discussion.