If that is the case explain to me how else monks make up for DPS. Have you even looked at the skill set that Warriors have. They are no chumps when it comes to DPS. Maybe I am off on my math skills but assuming a Warrior has comparable stats( I know its not going to be exact) a 150 potency attack is a 150 potency attack. So yes, without greased lightning and twin snakes monks would be just about as effective as a Warrior. I have 520 potency with my best rotation BS->True Strike->SP assuming that I am positioned properly for everything (I.E. an enemy doesnt rotate to face me while I am using any of the abilities). A Warriors top rotation is HS->Maim->BB with 630 Potency (or if we include Defiance and only apply the Maim bonus to Butcher's Block ~529). Maybe I am just bad at math but numbers dont lie.

GL is essential to a Monk being a DPS class, so I do not know where your facts are saying Monk can still out DPS all tanks even without Twin Snakes and GL