For me, playing regular Ops only gets a couple thousand but if I play Matchmaking I get around eight thousand. And the max XP you can earn per match goes up every week. So with a doulbe XP code and Fast Track, I was getting almost 17k a match last night.
When it was Episode 2 week, I was getting around 15.4k for Gargarin every 9-12 mins. This week I've gotten maybe 16.9k tops with double xp and fast track, but I noticed it's only if the match lasts more than 8 minutes.