**Spoiler Ahoy**
In Ashbury there is a quest that involves stopping the undead rising from their graves. Switch to real time and simply run between the three grave sites and there will always be a happy supply of fresh low lvl zombies for you to kill as long as you don't complete the quest.
You will lvl in minutes and while cheap and nasty, if you do find yourself in a bind because of your character build, this is a good way to sort yourself out. A couple of lvls in spot trap/disarm trap could really save you some grief later on.

A warning - if you level up too early, you will definitely max out and the end game can be boring.
Having said that - take the quest to find liam in Black root. when you get near the cause of the trouble, there is an unending supply of monsters to fight for unlimited level ups until you destroy the source.
You need to be a good fighter. Also, they are armor destroying, so you should take that off first

There is a level cap remover and a difficulty setting that can be changed

Actually, those void-demons aren't entirely inexhaustible. I've hunted them to extinction before. It does take a while, though--I think I gained some ~20 levels in the process. ;-)