Warlock boosting instance spec

Right now I am running my 62 warlock with a Felguard spec, but I want to be able to run some earlier instances with this character while I use my 70 T4/T5 level rogue for other instances. I figured I could swap "tank" toons in and out so each account can get some drops.

I am thinking that a solid affliction spec would be the way to go with my warlock, but I want to get some opinions from those who do some lower level instance grinding. I know the Felguard will be too much, so I guess it's back to the blueberry for a bit.

Would I be looking at a standard drain tanking spec or is there an optimal instance grinding spec?

I boosted with my 70 warlock and I did a SL/SL build and it worked perfectly.

http://www.wowhead.com/?talent=Iq0rVRbkoZbxczIizzes

I put the 1 pt in shadow embrace for PvP, so I use this build for that as well.

I bring out the blueberry and I have a cast sequence macro like:
/castsequence [reset=target] Siphon Life, Corruption, Curse of Agony

I just DoT everything up and put the VW on defensive. SoC and drain life as you like.
I never run out of mana unless I way overpull.

Let me know if you need more input! Good luck!

Edit: I also solo scholo/strat with this build.

It depends what lower lvl intsances you are going to run?

And for what purpose?

but most instances is easier with affliction specc.

but after you get seed of corruption, felguard collecting alot of mobs then seed , works wonders aswell

Affliction all the way.