I'm not sure if I'm imagining it or not, and I don't have any math or data to back it up, but I think Nullification Barrier counts all the damage you block as incoming to the caster of it. Last night whenever I used nullification barrier on Epicenter I would always end up hitting EXTREMELY hard afterwards. Highest hit was just shy of 400k shield slam. Not sure if that was simply from the high damage epicenter does in general or if it was counting me as taking the damage of everyone inside the barrier.
I was hitting so hard after barrier'd epicenters though that I would repeatedly pull agro from the other tank. Doesn't really help much in overall execution of the fight, but it was fun seeing insane hits coming across. Tuesday we'll be working on it in 25 man so we'll see if it gets higher there.