It looks like 769 would be absolute max worn ac on a bard; 674 without held items. That paladin's 538 is probably within the ballpark of what I would get with bis-ish gear viewing ac as worthwhile but tertiary to hp and resists.
If I count how many times I got hit for each specific amount of damage this is what I get:
Code:
37 24
5 30
2 37
3 44
4 51
9 57
4 64
4 71
1 78
2 85
2 91
3 98
3 105
6 112
4 119
5 125
3 132
1 139
4 146
It would be interesting to compare this distribution to a parse against a lowbie mob (just high level enough to have 20 distinct hit buckets*), and also against parses vs desired targets.
It would also be interesting to read the eqemu source and see if the behavior matches; if so we may have an exact answer there.
* I note I only got hit for 19 different values here.