I tried out Dirty fighting recently, i have allways played as scrapper and it works perfect and great damage output all time. The problem with dirty fighting is that you need to keep up your dots, and i experienced in flashpoints normal/hardmode that fights where you have to move around and sometimes get out of range of bosses, you loose alot of dps because you need to reapply dots all time. The problem is the range, i don't think it goes well with this kind of talent tree, too short. With scrapper you don't have problems with getting out of range sometimes, because we have only flechette rounds in close range and vital shot on long range, and we do not need to build up our damage like dirty fighting. Atleast that is my experience from lvl 50, i did defnately prefer scrapper over dirty fighting. I had hoped dirty fighting would be better since it sounded interesting. Also the sounds and animations on scrapper is much better done, and gives you the feel of being a scoundrel.