Surv hunters hit hard, have decent mobility with harpoon, and have trap which is pretty sick. Arms warriors hit hard and have charge, so they are more team reliant since they have less mobility. Outlaw rogue is great, which im sure you've already kinda found out. Sap/stun is even more costly, since there are less movement abilities to catch up after being cc'd, plus their slow has the same effect. They also have great damage and kick for healers and can peel for their team with slows/stun/sap if enemy isn't in combat yet etc. Feral druids are really strong for like mid encounters, since their spread pressure is really strong, which makes it easier to setup kills when multiple people are low. Ferocious bite also hits hard. Just make sure to apply/reapply finishers and dots/bleeds with tiger's fury, because when you moonfire while tiger's fury is active, the moonfire increases in damage. Arcane is really good too, since they are pretty bursty, allowing for quick kills, have good cc with polymorph and their aoe root. Frost is good too with more slows, ray of frost and other shit. So yea, if you plan on playing other classes, id say surv is really broken, arms is good but if you are playing against decent players who slow/kite and shit, it can be a pain and you can be globalled easily it seems if you overextend against good players. Outlaw rogue is great, just don't be afraid to sacrifice damage or even yourself sometimes for a play. (If arms warrior charges onto your fc and you think your fc will die, just open with cs and then spam slow so your fc can get away. You will likely die, but at least you kept your fc safe for a period of time). Idk, i've never competed in wargames and shit, so not sure if my knowledge is accurate in that regard but ya. Other than rogue, surv hunter, arcane mage, arms warrior, disc priest, feral druid and rsham can all be good. Prob better off getting other insight too though, and you'll kinda figure out which classes are good and which aren't from queueing enough.
