I'm gonna laugh my tits of when you actually try to CAST 2.5sec ish chaos bolt in arenas without being locked for whole match...
As far it goes from my play on retai: In 2s, doesnt matter you can be what ever you want (even guardian druid can 1 shot you on most private servers, just needs stamina +1 glyph+Bear hug=bam 90-150k dot each second for next 3sec) altho from burst classes for 2s....FERALS, Destro locks, wariors, frost dk's, hunters...rest are just as well fine since you wont be doing any **** above 2k with 2dps on good matches since there is no easy way you can kill good resto druid in mop..
3s....well in 3s you need skill and communication...LSD, MLS will be most playable combo again but there are a lot of combos like kitty cleave, jungle cleave etc that can perform rly well..
On end...pick what you wanna be: are you goona do insane pressure with dots for all the time or you gonna be doing insane burst at demand when needed, are you gonna sit on someone and making him cry, or you wanna support team with decent damage and INSANE survivability and HEALS when needed..
If you want easiest class..go warior, dk..
if you want decent burst in 2s vs 80% of ppl roll lock,mage,priest,war..
in general..you will suck royally in this game as always if you need someone to tell you what spec is "op" to play,,,
P.S. i've seen locks raping wariors 1v1 scenarios without effect of BF(battle fatigue) with ease..but ive also seen locks got eaten by some other wars..i've seen ferals soloing 3ppl. and seen boomkin holding a base of 4+ ppl on his back... just pick style you like and master it,...GG end of story