In an infinite TP situation where you have a threat lead, Fracture is worth using every 30 seconds. In a semi-limited TP situation, it's worth using every time Berserk is up so you only get boosted Fracture. In a very limited TP situation, it's not worth using.

There's no absolutes for those. ANY fight which you finish with more than 20 TP remaining is a fight where you could have potentially slipped in an extra fracture. Some fights have pauses for TP regeneration, some fights take longer with different group setups.

It's 100% fine to say that over long TP-starved fights, Fracture is a DPS loss due to TP starvation. But it's lazy and irresponsible to tell people to never use it, because in situations where TP isnt an issue, Fracture is the highest damage single target move a warrior has.