This ability will add 1.5 times more delay and 1.5 times more damage to your weapon. I am thinking about having this as a "melee stance" so the duration will be 2hrs and recast 30 seconds. Paired with another "magic stance" ability or some other sort.
The DPS will remain EXACTLY the same with any amount of Haste.
However TP gain goes from 13.9 to 20.85 (no rank considered) per hit. That makes a 513 scythe a "natural" 5-hit instead of 8-hit, which is 51,3 seconds between each WS instead of 59.85 seconds between each WS, at 0% Haste. The WS rates actually increases given that TP gain is scaled 50% up also.
This will overall give us higher WS rates and a huge bonus to WS damage.
Don't be discouraged that this will only "slow down DRK even more" because the differance between a 513 delay scythe and a 769,5 at 65%+ Haste is not that much of a nuisance.
As a bonus; it will be more easy going playing DRK in this mode. You can use spells between swings much more efficiently.