My Arcance Mage destroys my Destro lock in the dps charts. My 4.5 kGS mage gets about 800+ more dps than my 4.8k GS Lock. The mage with 36% crit procs a lot during most fights giving his dps a substantial boost.
Where the lock shines is having no real downtime, mage still needs a little downtime after a long fight which the lock can lifetap and is ready to go.