NCJim,
I sort-of do that.
Step 1: First I shield.
I open with a cast spell because the cast time doesn't matter. The mob isn't attacking me and if I wanted to I could open with a 10-sec cast... So I usually open with MB. Because SWP is an instant cast it is immediately ready for cast when MB is over, so I apply it ASAP. I then wait for the CD and put up D.Plague. Proceed to Step 2 or 2a
Step 2: So - at this point I've hit them with a nice damage spell and applied 2 DoT spells. Depending on the mob, I MAY wand it to death here. I NEVER use my actual weapon. I've lvl'd a mage and I know that even at the highest lvl, I'm lucky to TWO shot trash in VC with my 80 mage's staff... So I never ever use a weapon. I'll wand... This gets you back on full mana regen prior to the end of the fight. Which is good for down time.
Step 2a: IF the mob needs an extra spell on him, I'll drop Holy fire. It applies a weak DoT, but usually does great damage even though I'm Shadow Spec. You could mind flay, but I found that prior to 40, it wasn't doing great damage AND please note I didn't apply VE. With the shield up, I never needed it.
At 40, as this post originally started, I got Shadow Form. Since then, I've been doing this.
1. Shadow form
2. VE
3. SWP
4. Dev. Plague
5. MB
6. MF or wand
I don't open with VE then MB, because the big heal from MB is wasted as the mob usually has not yet hit me.
Occasionally, if I want to open big, I'll Open with MB, then VE, SWP, Dev Plague, MF (Cause MB is on CD), then MB.... But that's only if I think I need two MB to down the mob safely. 9/10 times I don't.