i have a feeling, u'll have to kill all 3 bosses like normal, it'll b difficult ya, but then as an extra boss, the 3 are combined, where they have 2-3 of their own skills, all combined into one:
multi legs from baal
ghostly glow (electric glow w/e) from mephisto
then diablo's signature build with the horns.
I mean for an uber u gotta fight all 3, u guys think this will b ne easier? shit, we have no idea how many ppl from blizzard actually play diablo, then for them to see how we run thru gubers soooooo quickly and easily, they want something that wont b a walk in the park, something u actually gotta work on. something with like a 9:1 ratio, 9 of our deaths to 1 of theirs, i mean its just a random ratio. Knowing blizzard and how they design the diablo games, the ration is probably alot higher then that.