regarding Fracture, here is a spreadsheet with a rotation over a period of 54 GCDs
total potency gained is 85
or 1.57 potency per GCD
google doc spreadsheet

so, over a period of 106 seconds (2 sec GCD assumption, 3 GL stacks)
you do an extra 85 potency attack, or like 100 to 200ish more damage, assuming PERFECT weaving of Fracture, no clipping and close to 100% uptime.

worth it?