Without dispels or CCs on the Mage during DF, Frost is amazing.
Notice the pattern going on here, with Mages having a slight disadvantage with CC and Warlocks with dispels.
Okay, so Scorch and Mage Bomb (Shadow DoTs) proccs FoF and BF (Mind Spike and Mind Blast proccs), except our everything is reliant on Proccs. (Shadow Priest is mostly from DoTs).
Notice the pattern.
Also, one FoF isn't going to do crap. The only way to kill someone is in a DF.
Frost on the other hand... Not so much. Yes, if we have PROCCS, we're quite mobile, but Scorch and Mage Bomb alone will not yield good results. The only way to kill someone is in a DF anyways, and we'll usually just get CC'd or the DF will be dispelled during.
Regardless, this is trailing off topic. This thread is about how Blazing Speed's current PTR build will be replacing Blink and what happens because of that. Our rotation in PvP is an entirely different story.