which char to focus on for PVP and Why?

shads are decent, boomerang step with shadow partner wrecks.

Shads are pretty good in PvP, both Bstep / assulter are good. And venom can activate as well as smoke.
Smoke doesnt show up on screen but for a small amount of time you get its effect. Also CD on skills get reset after death.

Pallys are beast at PvP with decent damage and tank skills/hp. Or Fast chars, i think a NL would be great at PvP but i didnt test that yet ;p.