I have been pure tank since 20, and I love it, kinda forced to use Quinn but I can live through all battles with add on's. With Vette I can speed run through quest that require me to kill certain numbers, with little down time, while switching in Quinn for Boss/harder sets ( where there is the tougher guy that walks around near a set of mobs)
At level 40 right now just completed ACT2 was able to do some quest 3 levels below