It is just too short to be a full game.
The Role playing ellements are "supressed" in this installment but you can have more units , giving a more strategic character in the game.
The misions on the campaign are 95% the same for all factions, only the dialogs change. A thing that reduces replayability dramatically. After you finish the game once and pick another faction to play it again you stop very early cause you get bored of doing the same misions all over again.
Tha game does not provide any challenge since you can finish it with even only one Hero while the rest of the troops sit back (and drink a beer or something...)
It is also very very short. You can finish it in 1 day...
It seems that it got out mostly to support the multiplayer side of the game and the single player fans will be a little dissapointed...