With Thief, the game is designed to be played as a Thief class. Deus Ex and No One Lives Forever 2 can be played as a Thief, Warrior or Wizard (Hi-Tech). I'd like to see RiftRunner have provision for any of these classes, including cross-class. If a thief could have skills that provide high mobility and a slow but powerful Backstab skill, I think the Thief might be worth playing.

I know there are no classes in RiftRunner, but to successfully play freeform-skill games, you need to at least specialise somewhat in one or two stereotypical classes. Hence it does have classes, they're just not rigid.