In WoW, all of the tanking classes have a "threat modifier" for when their tanking, whether it be passive or baked into a skill you have to activate. Basically, the more damage you do, the more aggro you make. But if a melee/ranged gets 110%/130% of the tanks aggro, the enemy switches to them instead.
How does WoW tanking work? In FFXI, there's a "enmity aka hate" system and it's pretty awesome. Warriors get the skill Provoke which simply causes a lot of hate, and most Paladins sub job WAR for it so they can hold hate despite their low damage. PLDs also get a lot of hate and defense boosting skills.
Sooo, our version just got third jobs today, which is at 140. kLT is getting episode 8, which includes 8 person parties, new instance dungeons and bosses, loads of new gear aaaaaaaaaaand a whole new tanking system! <3 Monsters now aggro based on who's doing most damage, and it looks like Knights have a new skill. I think it's a provoke.