yes what yoyocheese said. also, if you have friends, get a group of 4 people so more monsters spawn, and then you can get more exp/hour. Also, utilize the absorption potions and overloads.
Like mentioned above the only way you'll be able to chin is with the absorption potions at nightmare zone. Grab a group of 4 people and enter a melee only boss zone. The absorption potions will take damage for you and you purchase them with nmz points.
Chinning at nmz is the best way since they bought it out, especially with the absorption pots and the overloads making the bonuses go through the roof.