So, I'm currently running a bunch of heroics with our feral druid, who used to be a disc priest with a off-spec of shadow. He's one of the kinds of dudes who knows everything about every class and spec, and so we were talking a bit about the shadow changes. He said that he had been trying out shadow DPS on the PTR with a copy of his priest, and with a pre-made character.
He asked if I had dropped mind blasts other than ones after casting VT. I was like "Wut? no I'm not dropping mind blast." Cause I read that you need like five billion haste to drop Mind blast. (I also tried it out for myself a few times. Granted this was like 2 major patches ago, but I'm just saying it's not like it's something I just read and just believed without testing it for myself.)
But he said that he tried it out where he only casted MB after recasting VT just to proc replenishment, and it resulted in a ~400 dps increase on both characters he tried. He also specced out of improved MB and put the 5 points elsewhere. He said on his priest copy he only had like 400 haste too. I'm at 488 right now. HMMMM
If nothing else, it's worth a try on the test dummies. Remind me to try it out after work tomorrow.
If it DOES turn out to be effective, it's going to take a while to re-train myself to not use MB every time it's off cooldown. I've been raiding with my current 'rotation' (and this word is used loosely) for a year.
Here's the thread on Shadowpriest.com about why you should use mind blast: http://www.shadowpriest.com/viewtopic.php?f=61&t=24328