Ravnica at War is going to be nuts.. 4 mana to
exile any multicolored permanents is going to hose a lot of playable cards that will become unplayable especially in standard.
Then the planeswalkers so far that have no way to uptick themselves besides Ajani with of course the minus ability just turns them into so far meh. Liliana can't even hit her ultimate without Ajani possibly helping so far. Oops we do have proliferate so it may not be a bad thing if planeswalkers can't hit ultimates.
Amass looks like a very interesting new mechanic. Gives you at least an
opportunity to start an army if you don't have one yet with a zombie token