For a casual player interested in wpvp there is no safer bet than warlock.

Mages and rogues? Strong but heavily reliant on skills with cooldown to stay alive. Knowing the order of skills will make or break the fight.

A warlock will fear, dot and run. If the first fear, for any reason, breaks you then cast Death Coil, the strongest spell in the game, fear again and, for good measure, cast a shadow bolt. Congratulations, your target is now dead.