So lets compare 2 pieces of patch notes for Clockwork City DLC
Stinging Slashes (Master DW): Increased the damage bonus to Twin Slashes’ bleed to 1500 each tick from 516.
Destructive Impact (Master Destro): Increased the damage bonus to Destructive Touch’s direct damage to 1500 from 516.
What's that means is Twin Slashes will get 1500 dmg to each tick which overall adds 7500 dmg to whole skill while Destructive Touch gets 1500 dmg buff. Lets not forget that Twin Slashes is over 2 times cheaper then Destructive Touch and deals bleed dmg which have 100% penetration. Even after adding that 12% cost reduction to Destructive Touch it's still 2x more expensive so other additions like stun/immobilize etc are on place for higher cost.
Both skills have 5 DoT ticks. Comparing how this weapons will influence DPS it's raw 750 DPS increase for dual wield when it's ~190 DPS increase for Destructive Touch. I would be glad to see Destruction master staff buff beeing reconsidered and maybe changed to add 1000 dmg to each Destruction Touch DoT tick which would be over 600 DPS increase. For now when we look at Malestorm and Asylum destruction staffs there is no point to even consider using Master destruction staff.