Fracture is a DPS increase for Warriors because they have a trait that makes it last 30 seconds and thus it's a 300 potency attack if it ticks the full duration. It's their highest potency attack outside of Fell Cleave at 54.

For Paladins and other classes that use Fracture via the Cross-Class system though, they get it at its base value of 18 second duration so it's only a 220 potency attack. Therefore it's a DPS loss to use it as their other skills are on average higher potency.