Here's a good summary of the attack/defense system in EQ:
http://eq.knowledgepit.org/wiki/Melee_attacks
So, first we need to define the problem. At lower levels it seems mobs are hitting for more than they should, or rather, the DI is rolling high compared to what it 'ought' to be, given a player's AC/def. Max hits by mobs land too often, min hits too seldom.
Next task should be quantifying this. This involves parsing, obviously, and is much easier for someone with GM powers to do, since they can change levels / summon gear easily, so I'd recommend doing it on a test server.
Multiple classes.
Levels 1, 5, 10, 15, 20, 25, 30, 35, 40, 45, 50.
AC: Naked, +100, +200....to softcap.
Mob: low green, blue, even, yellow, high red.
500 swings of combat or so.
We can pick a few values of Level/AC/Mob, and test the effect of agi, and see if it's in-line with expectations.
That should be set up in a nice table, organized by DI and max/min hit %. It could probably be done in a day or two.
(This is bringing back memories of my job in QA...)
Next, knowing the state of things, we should compare this to classic, or even live-EQ parses if no classic ones are available, to see what needs to be adjusted.
Adjustments can be as simple as tweaking AC/ATK values on mobs and players, or as thorough as a new attack/defence formula for the lower levels. Once the evidence is in hand, a decision has to be made here, and I guess that's where our friendly devs come in.