Thinking about it, the most simple explanation is that there is probably no "mob level cap" on AC but a floor value where AC can't squelch the DI portion of the calculation any lower, which is why you'd see a seemingly hard cap on AC even though there is only supposed to be a soft cap way above observed values. Also explains why AC buffs do nothing and why avoidance shines.
Like, on the storm giant escort you still get the full 1-20 bracket and the full damage range but wether you have 200 worn or 400 worn you're almost only gonna random 1 past 200 so it seems you're hard capped but you actually just can't go below getting a whole bunch of minimum hits with some small randomness thrown in.
|