You ever been on that House of Thule raid where the add mobs grab you and pull you around like they got you by the back of the neck and you can't run away and it drags you every where and you can't cast and you are tethered to the mob? Yeah, that's "slow push." I suggest you fight him mounted so it doesn't move, otherwiese, your casters are going to have a LOT of interrupts when they get hit with this. I dont think it's AOE, tho. Or has a very short range. My chanter was in the back and it never hit him. Necro got tugged around a bit, warrior got hit, but it didnt really do much to him since he was mounted.