This is exactly the problem. Before, you could do a huge PvE battle with lots of AI and friendlies and end up getting 1-3k xp. Now, you can't. Those huge PvE battles were fun as hell, always different, and enjoyable if you played in a clan/group setting. Now with missions tho, it's dull and repetitive. You are playing solo, for most efficiency, and get 1 of only a few predetermined sets of enemies for the fight. Before the wipe, I couldn't put the game down. Now, I want nothing more than to just get off and go play Rainbow Six for a few hours.
Hopefully when they re-implement the kill/assist xp, it makes PvE fleet combat a viable leveling strategy. We need something other than missions to be reliable leveling method.