It's not particularly slow, but it's definitely a dull affair.

I feel like there's not a single source of experience that is actually fun to do.
You're either kicking puppies in the open world, or you're kicking puppies in an instance.

At least in instances you occasionally get a puppy that bites back, but even then, it gets dull after a while.

The leveling experience in this game is just really uninteresting.