We need more things to do, we have little content and we spend many days and weeks with nothing to do. I am sure there are a lot of good ideas around that could be created, but I can recommend some for now:
CO-OP Bosses - A group of 2, 3 or even 5 players to kill a very difficult boss.
CO-OP PvP - Like a duo, each player places 2/3 heroes to fight other two players.
PvP 3x3 heroes - A smaller team PvP to increase the options.