I went there with my 20s. From 20 - 30 it was a lvl in 3 runs. After 30 add like a run or a half a run to each to lvl so 31 is 3.5 runs to lvl, 32 is 4 runs... etc. At 33 you get a quest that should get you a lvl (have to run all three sm and turn in). At 34 the xp at sm takes a drop because 1/3 of the mobs there are around 36 and the other 2/3 are 38/39 and the bosses are 40.