You need to work on the quest experience. At level 41, I got 2-3% per quest. I did all of the quests in Hinterlands, Tanaris, and Blasted Lands and only got about half of a level. :/
this game was ridiculously challenging because guards walked past my hiding position numerous times! 2 guards walked past the same position 9 times and I cloaked each time, but on the tenth time I was out of energy and they saw me! A great waste of time, and a pain to complete. Whoever created this game needs to rethink their maps, and how the guards react.
endurance mode is tough, you have to play the games multiple times to understand what to do, and for some I couldn't even figure them out after several tries so i just mashed buttons.