Ganking people who are just grinding away in their PvE gear is doable as a 0/0/0 spec. Arenas are the main focus of WoW PvP, like it or not...
Oh, and about Warlocks dominating casters...ever had a matchup against an equally geared and skilled frost mage? Ouch... And most PvP geared healers can just outheal us until reinfocements arrive, or simply run away, because they aren't gibbed that easily, even with a full row of DoTs and CoT.