Fracture has always been a DPS increase. It was out of favor in 2.x due to the TP cost. Thanks to having both a 400 TP restore, and a 300 TP restore, many say that Fracture is now worth using.

Personally, I like to use Forbidden Chakra while buffed with IR, BfB, and BB. That is also about the only time I like to use Fracture - it's not a big enough DPS increase for the TP cost otherwise, IMO.

You should be at 5 Chakra stacks when you start an encounter, for use either in restoring 300 TP or in using Forbidden Chakra. The only time it is worth building stacks mid-fight is if you are forced out of Melee range to avoid an AE, or if the enemies pull some disappearing act on you.