leveling is easy, just take enough bloodlust and make a full dps build
psi has the best burstdmg in the whole game and can be also played as massive dps in pvp, however survivability suffers then
in a few days when nw patch coms psi still can be:
dps
support
controller
from my experience, psi is "the best" class for pvp (even though there is no such a thing as the best as all classes can be played in PVP spec) as it can almost infinitely lock down its opponent while still damaging it and even if mana is empty there is a skill to just refill it while beeing very endurant
and if an enemy is superior you can put hypnosis on him and just get away