I think it's going to be hard not to run Abzhan or Mardu. With Utter End, being printed (someone called it utter death earlier >.>) and the Siege rhino with ETB each opponent loses three life you gain three life, and Butcher of the horde at the top of both mana curves. Mardu will be a rough aggro match up for a lot of players, Turn one soldier, turn two raise the alarm, turn three Goblin Rabblemaster, and then butcher? That is a pretty unstoppable dream curve. Abzhan really just has to rely on some nyx fleece ram life gain, and then dropping Anafenza and a rhino and turning cards swideways. The biggest issue here is, if the next set has cheap board removal, or some izzet player gets frisky with polymorphist's jest and scouring sands both of these decks take really hard hits. I don't see that happening competetively though, but weirder things have happened.