If you are soloing the sheep, in one of the good spots, the sheep could give decent exp/hour. At level 40 each sheep cave me 250exp. The only problem is I was never alone at each of the big spawn spot as there were people there farming for fleece (easy to tell, if they are lvl50, they are farming :p).
If you are in the area and in need of levels, the best would be to join a FATE party. I assume these happen on NA servers. Up until yesterday there could be 3-4 full FATE parties running around (xfers, didnt seem as many people in the area last night). In a FATE party you get cred for killing the target mob(s) and usually the max reward at the end of the FATE (10k+). If you do the 3 part one, you easily get 50k (there is an escort, and fight a bunch, and then a big dragon to end it [it alone will give 20k]).