I only had a chance to do this on test server so far. Everything was camped on the real server
[You must be logged in to view images. Log in or Register.] .
lvl 50 bard vs a green but almost lightblue mob. lvl 30 mob.
Test server.
757ac = 64 23 16 23 43 48 48 31 16 48 16 9 48 18 46 51 53 16 31 46 31 28 61 33 61 61
650ac = 64 16 16 43 48 16 43 56 16 58 16 58 16 43 64 64 18 64 48 58 58 16 36 51 26
587ac"lowest i could get naked" = 43 64 64 64 64 11 64 51 64 16 64 21 16 64 41 16 16 16 64 21 21 64 64 64 64
This was against a green but almost light blue mob. I will have to do the same test on the live server to see the difference. Having over 700ac seemed to help mitigation a ton. It could also be that It is only reading the ac you have from equipping items. It might not be taking into account the 587ac from defense and agi and natural ac. The mitigation might only be coming from the items you are wearing. No idea but when i dropped 170ac i got hit wayyyy harder from a green mob. As if I had 0 ac.
I will keep testing when at all possible on different characters. Going to test this xp out now hehe. : )