I have two full t4 dts an old one(2009) and a new one(late 2011)
I recollect on the new one delibaretaly chosing the 1.answer on destiny quest (attack rating that is if i remember correctly)
while on the old one i have made a mix of answers.
Now both of these toons naked in the same specc with no aas on, have 22.6 dps in def and 25.smt in frenzy with base stats identical(strength,con,wis etc) They have identical regenerations as well.
The thing is on the old one when i undressed him it kept showing me 35.6 dps in frenzy and 31.smt in def.i had to make an area change for the numbers to stabilize(relog didnt help either).
Now the weird part is that if i dress them with identical armor/accesories the new one keep showing a 0.2 dps benefit in stats.it is ofc neglactable but there.
Now on the issue of great aggro of new/less geared tanks dont forget the hidden 'dmg' aggro coeeficient meaning a tank that takes more dmg in general generates a bit more aggro.