There are a few features/problems I would consider game killers, currently.
1.) The inability to share between Friends/ Guild mates.
2.) The inability to share credit on Identical missions. Having to play the same contract twice with a friend, is not fun.
3.) Ninja Looting. The ability for friendly units to enter (what should be) a private mission/instance and capture/sink a vessel that a player or group of players have been working on. Not to mention the ability to interrupt a friendly player from Capturing a ship is ludicrous. This is griefing.
(4.) IMO there are few things that encourage players to play with one another. I am not talking huge units, there is always a benefit to that. I mean, small groups of 2, 3, or 4 players. Why play together? You cant share, you don't get equal XP/Gold, and nothing is keeping a rando from busting up into your match and stealing your shit.