Word.
I sort of understand the 'turret' comments, but not entirely. Sure, there are moves you have to hold still for, but many are instacast I'm healing specced, and besides holding still to do rapid scan and healing scan, I am running around either healing or targetting an enemy with blaster fire or a missle.
Now, you could say I'm only level 29 and don't even have tracer missle, so what do I know? Well, even if I had tracer and were arsenal specced, I still would be mobile because that is what many pvp situations require. I think mercenary is pretty versatile.
All that said I am very interested in rolling a powertech to see the differences for my self. Melee combat as a bounty hunter would be interesting.