you should start running Phantom of the Depths, it's around 2,5k exp per minute if you know how to do it. And the best part is that the exp is really high, so you get like 40k out of it.
Co6 is brutal as well, many parts have over 2,5k exp per minute, and you'll pull out around 70-80k exp total out of one quest chain.
Of course, there are just way too many quests in these level ranges, so there's really no problems getting to level 13-14 without wasting any good quests. It's just a suggestion to get to those levels faster.
Spliterskull is also a beast for level, you'll get well over 1k exp per minute and there's a lot of exp to get there.
As has been said above, durks is amazing, 2 man it's about 1 minute between each runs (that includes both rcing, taking window, etc).
Stealthy repossession is even better.
It's worth doing gwylan's 3 times per character if you know how to do it. Me and Yar two-man it in 5 minutes, which is over 1k per minute.
The pit is quite nice as well, 10 minutes for 10 exp. On elite it's about 12 minutes for 16k exp.
Not the best exp per minute, but because of the large amounts of exp, it's well worth doing.