Its easy to play ok, but the skill cap is very high!
..that's the same with any class lol
as he said though rogues are good with pretty much any other class in arena and they are great at 1v1. rogues are great at CC at 39.
however just about any class/spec can be played at 39 in WSG, i guess here's a general rundown
warrior: great burst, suseptable to CC, intercept is a key ability. defensive spec is good for FC
rogue: excellent CC, a bit reliant on CDs, effectiveness gets worse as the battles get larger
paladin: ret can be kind of good DPS, holy is the most mana efficient and probably best in survivability out of all healers, although very immobile and no instant casts. prot is good for FC
hunter: range+instant casts is very good, quite a few different CC abilities to use, suseptable to LoS.
shaman: probably the most well rounded class, playstyle is determined by spec
druid: very bursty if played as a healer or caster, mana is the biggest problem. feral is good for FC
mage: probably the most interesting class (IMO), good CC and escape abilities as well as burst, but suseptable to burst
priest: probably the most versatile healer, lots of instant casts + dispel, an essential part to any team
warlock: can either be played as a glass cannon (dot dot dot) or soul link (lots of survivability, 1v1 capabilities, burst is minimal).