With enough mobs, it's probably a dps increase if you're in a pull long enough that you'd run out of tp without doing this. As far as how many mobs it would take for that I don't know, but it should be easy enough to calculate. Figure your damage per tp cost based on a set #, include the time it would take to run dry on tp, change the #s to do what you're suggesting, see how it adds up.

You're definitely onto something though, if you get at least 1 more useful rockbreaker out of it let's say vs 10 mobs, that's 1300 more raw potency before modifiers vs 190 from true strike.