I recently equipped a helm that increased my monk's crippling wave damage by 10%. The displayed DPS did not change nor did it change when i swap out crippling wave for a different skill. Is this a known issue? Is there another way to determine the DPS when using an item that increases skill based damage.
No, the Damage attribute on the character sheet does not take into account skills or equipment that boosts particular skills at all. You would need to determine the DPS yourself, following the formulas at How is skill damage calculated based on weapon damage?.