Mindflay
We’ll look into it. I don’t have the bug list right in front of me at the moment. (src)Warlocks were designed to have high dps while Shadow priests were designed to have much lower dps. They were a utility class that paid in dps in order to justify their amazing group benefits. With the buff overhaul, we improved Shadow’s dps significantly. (We also dropped lock survivability in PvP too.)

Just an update:

Mind Flay also get canceled when the target uses a PvP trinket (or when druids shape shift, or various other abilities that remove snares), even when we have the glyph of mind flay. I know this is because of the snare effect, but with the glyph, there is no snare, so the spell should not be canceled, right?
The problem in this case is that the glyph did not remove the snare — it just set the effect to zero. So the trinket etc. still could cancel the spell. Because there is no easy way to have the glyph remove the snare component entirely, we recently made a change so that the glyph instead lowers the snare to a very small percent. (src)

Shadow priest design
The Shadow priest design in BC was a cool one, and by and large it worked. We feared though that we were reaching a point where having multiple Shadows was going to be mandatory for any large raid. Having multiples of one spec (of a class that was probably already going to be over-represented because of its healing potential) risked pushing some of the other historically under-represented specs( Survival hunters, Ret paladins, Balance druids, even Disc priests) out of the raid. (src)

We rebuilt Mind Flay to make it work under the new system. It’s now much more like Arcane Missiles, so the possibility does exist you can clip some of the ticks. It’s possible for us to rebuild the spell again, but that will mean changing a lot of talents (which introduces the possibility of bugs) so we need to make sure this is absolutely necessary first.

Can anyone else comment on Misery falling off? It could get overwritten by Improved Faerie Fire and if you’re playing with a sloppy Moonkin, it’s possible they put the debuff up and then let it fall off. (src)