I'll echo how fragile I felt as a Thief. I think I spent most of my time just using dual pistols for the sake of not getting destroyed in all the random PvE stuff I was doing. Which was fine, since dual pistols is pretty fun.
Only did a few matches of structured PvP - seems pretty fun. I could say "x class seems ridiculous" and such, but it would be entirely meaningless considering my limited experience and how I pretty much had no idea what I was doing, haha. I could definitely dish out some damage with dual daggers if I got the chance, though. Just a matter of learning how to do so properly.
Overall, it seems like a cool game. Certainly would like them to fine tune stuff a bit (which I would think they are very much doing), but on paper it all seems great and in practice it was fun.