Ok ya the high tier mercs t3 to t5 are the harder to get usually you have to know someone high enough to run you through the unlock quests or pay someone too run you through the quest and its not cheap from what I use to charge was about half a million plat plus also I made a mistake have the T5 mercs on my guys not the T3 like I said been awhile but just peaked at them yesterday here is the guide i used for the mercs.
http://articles.eqresource.com/mercoverview.php
Also just FYI the diffrence between Tier 1 - Tier 4 and Tier 5 mercs is very huge btw the T5 mercs can solo raid targets that are outdoor zones since mercs don't work in closed raid zones example (can't do 2.5 epics with mercs since the
Dreadspire Keep: Demi-Plane of Blood is indoor raid zone.)
Also some other useful links for mercs sure you could find them yourself but just to help out since information is fairly scattered. These links made coming back and learning how mercs work and what they could do really easy.
Everything about mercs stances/upgrades etc
http://almarsguides.com/eq/general/mercenaries.cfm
Bottom of page has most the race/class combos for mercs
http://everquest.allakhazam.com/wiki/EQ:Mercenaries
Only big things I am not sure how ya would figure out is T5 mercs obviously have AA bonuses the clerics heals amazingly and the tank merc hardly ever take a lot of damage even against raid targets so not sure if there is a way to figure that out also since merc armor auto upgrades as you level up (you can see the armor change per couple levels) not sure what armor and weapons they change to as they level up with you. I guess I could see if I took a alt and power leveled it up at what levels it changes and take pictures of it but not sure how to get the stats of the armor they are wearing or what they are wearing.