Random... Flurry, AE Ramp... hits max 2200 - but mostly 900-1k but is not slowable so be prepared... also it can stun so agro can go a little goofy... watch adds from walls.
I didn't see any rampage messages for the short while I tanked it with dodge disc. This is probably normal, but hits really fast, got about half of melee spam window filled in the 18.5 seconds I had aggro. Max hit I saw was about 2k with some shielding.
It is not AE rampage, it is every round rampage (think ssra) single target. Also, for now at least there seems to be no range on it, people were getting rampaged from across the room well outside melee range