Hey Transfinite,
I honestly haven't dabbled with Fracture to much, but from past experiences, it usually lowered your overall DPS and wasn't worth it.
I'd follow up with somone more experienced in using it.
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From patch to patch fracture seems to jump between bad and tiny increase if used perfectly with a dps loss if used wrong.... so personally I just don't use it.
As RocheKat mentioned Fracture upkeep changes per patch and SS build. Generally fights that give you nearly no downtime like A2S you will want to not use fracture. Other cases I go off of SS build. Builds that would have low to mid 5XX SS from last patch I could fracture regularly every few DK rotations with healthy TP. I haven't reached the high 6XX to 700+ SS yet but as I start leaving 5XX I would only time it when B4B (or use it over ToD if the timer is a better fit for how long an add is up). At this point though if a long fight doesn't give a fair amount of downtime at that high SS best not to use fracture.
Without a nin in any fight that has more than 2 min uptime and with nin any fight with more than 3 min, I won't use fracture except during the opener. Fracture is a DPS increase if you don't drop anything, it can be used every other demo rotation so that you won't clip the demo dot too early, especially with the high amount of SkS we are forced to have it will help though TP is a big issue.
UPDATE (10/26/16): Added some new details and reworded a few sections.