Caster: Elemental Shaman or petless (GoSac) Destruction Warlock. Avoid Moonkin and Demonology Warlock.
Melee: Frost DK, Retributuon Paladin, Arms Warrior. Avoid WW monk, Sub Rogue and don't even touch Ferals.
Healer: MW monk and Holy Paladin. Avoid Resto Shaman, unless you wanna die alot and be completely dependant of your team mates.
After duelling around 50 people in Elwynn Forest and subsequently losing 50 duels, I have to say I didn't see any damage going off automatically. I don't know if I was doing it wrong, but I stood still and following your advice: I didn't use any abilities.
In seriousness: one person said Elemental o/ pretty hard to believe to be frank, I'd say Elemental is currently the easiest caster in arena (with Hunters being more enjoyable to play, but not easier nonetheless).
To be perfectly honest, Hunters are by far the easiest class both PvE and PvP. Always have been and always will be. It's the 'noob' friendly class. Anyone can be good at them, thats why they're the most player class I think.
IMO this is only true since they removed the dead zone for ranged attacks. I remember playing hunter when there was a dead zone and it actually took some skill.
Now hunters are ranged-caster-melee. Ranged instant interrupt. No cast time on most attacks. Attacks with cast time can't be interrupted with kicks. Etc.
If anything they're a little squishy, but definitely noob friendly. Also very skilled hunters are scary to play against.
Warrior, definitely.. Easy peasy, lemon squeezy.