yeah i was doing it with a friend yesterday although not highly effective it still works to some degree, my char the higher lv one aggroed a few lv 14s, and my friend just killed them as they hit me, but i took only 1 dmg from each of them and they missed me most of the time, its not really powerleveling but it does give the lower lv player the chance to lv faster than usual. I tried all the level share and i also tried killing a mob so it had lyk 1hp left and then my buddy just finished it off, but he got barely any XP, i think the xp in ep2 is based on how much of the mobs health u have taken of, so if i take 50 % of i get half xp, not sure if thats true but it seems the case.. hope i helped a lil :P
{EDIT} oh and i think that being a party and doing this technique doesnt work well enough, if u dont understand my paragraph before lol (messy n all over the place ) pretty much the lower level char is just leeching your mobs off you :D