Having potion up for fracture is probably around 5% gain from 300 potency, which is like 15-ish? Don't forget that the 20 potency gain from butcher's block combo is also buffed by potion/internal release. As Spooky said it's pretty much a negligible difference. I use the rotation I posted earlier mostly when I pull the boss or when I'm with DF tanks who stay in tank stance very long so aggro is not an issue. If there's even a remote chance that you might have aggro issue, butcher's block is never worth it.

Another good example where you can use that rotation is where there are mechanics that reset your aggro, such as a7s jail or a12s timegate. I can use butcher's block quite often in a12s since I'm holding boss aggro until after first stasis, and after timegate I'm back to 0 aggro. In other savage fights, not so much.