Nightbane

[Lissa]

You're going way crazy with the Heroic mode instances, Bolty. While the mobs DO hit hard, I've never had any mob (or even bosses in their enraged state) hit me for more than about 4,000 or so in a single hit (well, I've had Capacitus hit me for 5700 during his brief enrage.) Even on pulls where there's more than a couple of mobs to tank, I can usually secure enough aggro to keep a peel from occuring after the first heal. I haven't yet done Shattered Halls on Heroic (I've primarily been corraled for Mechanar and occasionally some Slave Pens), so maybe this is where you're seeing hits for 7500 (the gladiators, maybe?) I still think that you pulling aggro on the first heal is the tank's problem, not yours, however.

How many mobs have you had hitting you and how much CC did you have on those runs? Try some of the other mobs in other instances like the Bog Giants in Heroic SMV, 3 mobs hitting you at once (like Heroic SH, the guantlet at Murmur, areas in Botanica, and Sethekk Hall guards) and see how much damage you take then. Your basis here is pretty limited as Mechanar and Slave Pens are considered the joke heroics compared to others (I've heard Heroic Mechanar referred to as Tokenar).