How well a tank holds aggro depends entirely on the tank's equipment, skills (i.e. Masters vs Adepts vs Appren) and personal skills. So, yes, you are over-aggroing if you grouped with a tank that cannot hold aggro; and no, you are not over-aggroing if your tank can hold aggro. I tend to exclusively group with certain tanks who can hold aggro, while I chain nuke BSS and Nil Distortion and the Noxious Bolt training spell. I always leave groups with tanks that cannot hold aggro, even when I am exclusively casting only BSS and no other spells. The main problem is this - tanks tend to focus primarily on their equipment (at least thats what I gathered from the tanks I know) before they even begin to look at their skills. An Apprentice Taunt can never outaggro an Adept nuke. Some food for thought....