Play League of Legends, it's uber easy to balance the game and has some of the best fast paced and skilled pvp, there is no button mashing just clear and concise tactics and play methods for each character.
I'll admit that to start with you are gimped since you wont have Runes etc, but a good player can overcome that and pwn.
It's not an rpg as such but has instant queues and easy to understand gameplay with minimal system requirements. Me and the guild play it when we aren't on WoW - just don't go afk or ragequit a game as it's almost an instant ban.
You can put some money into it if you want some extra champions otherwise you get a small selection which rotate each week.
I don't advise Rift, I played it alot and aced the first tier without much difficulty, it is a mixture of Aion and WoW - taking the very worst from Aion and the best from WoW...unfortunately the odd combination results in a crud game with no content and PVP which is just dire.