well.. i recommend you try GeorgeS npc editor.. it is very good, and you can choose specific zones where you want to change the aggro radius.
link dedicated to his tools on this board.
http://www.eqemulator.net/forums/forumdisplay.php?f=674
sure there are many sql queries you could run to accomplish the same thing.. but running one all inclusive one will change things you are not wanting! (i think) and, before doing anything, i would make a backup restore point for your database.
i would do it something similar to this.
UPDATE npc_types SET aggroradius = numberyouwant WHERE aggroradius > numberyouwant and zone = 'zoneshortname';
first numberyouwant.. would be what you want to change it to. by default, i think most of mine came at 40. i would check your table to see what yours is.. so, in my example.. if i wanted it to be 30 in crushbone.. i would run something like.
UPDATE npc_types SET aggroradius = 30 WHERE aggroradius > 30 and zone = 'crushbone';
im quite new at this, so someone might have a better answer than i do. remember to backup your database before doing anything!