Fracture for WAR is always a DPS increase, even if you have to double-eye to facilitate SE upkeep between using Fracture and Fell Cleave.

If you have to double-eye, Fracture is a DPS increase of about 22.2~ potency, whereas if you don't need to double-eye to sustain SE, you are gaining 49.96 potency from using Fracture (whilst otherwise rotating SE/BB normally). All these numbers are after the usual modifiers (Deliverance/Maim/SE) and with dot interaction accounted in for (ergo, only the initial hit being buffed by SE, not the dot component).