I'm using my (not very well geared) lock to boost my toons. Get the 51pt demonology talent, and the VW glyph and you're all set (at least up through ST, that's as far as I've got at the moment).

Use the VW to round up the mobs, then pop a few SoC's into the group, pop your trinkets, gogo demon form immolation aura and bingo - dead mobs all around you.

3 min CD on Demon Form means that by the time you've LifeTapped, and let Fel Armour give you a bit of health regen you're ready to send the VW to round up the next bunch of mobs.

I can do SM cath in 3 pulls (not quite prot pally speed but a lot better than it was for me pre-patch), doing the lower courtyard, upper courtyard and then pull Mograine and the rest of the cathedral in one go. This usually takes around 15 mins (more if I'm looting). I've only just got the VW glyph and the 20% health is certainly noticeable in his ability to last while you round up as many mobs as you can. Also once you start damaging the mobs he is healed up to full so there's no need to wait for him to consume shadows.

RFD is also done in around 25 mins (if I dont stop to loot anything), with ZF taking a while longer as those pesky mobs heal and are not so nicely grouped.

I think I'm sitting at around +950 DMG self buffed (no food or pots), with just over 10k health.

I'd certainly give it a go to see how you get on, especially for any of the above instances.