You can use your warlock to do some serious instance boosting since the patch. It'll still be pretty fast without RAF. They significantly raised the AoE caps, rain of fire can crit and you can cast it with a million mobs beating on you, and immolation aura does about 700 damage per second to an unlimited number of targets and can't be interrupted. Don't start with DM by the way, it's too many pulls, patrols, winds around... not a good boosting instance. Do SFK or Stockades.

Here's what I did:

Get glyph of voidwalker for 20%

1-10 Quest

10-22 SFK, can be done in a single pull - put your alts behind the gate.

22-30 SM Armory - 2-ish pulls

30-40 SM cathedral 2-3 pulls. Best part is you can pull the entire cathedral room at once now. Send your VW to morgraine, pull him back, metamorph and pop immolation aura and rain of fire and kill the entire room at once. it's wild

40-46 ZF. You can pull 3-4 rooms at a time, just train them back to your alts and seed of corruption there. Graveyard - sacrifice a vw, open all graves at once, blow up with metamorph. Stair event - single pull

46-60 UD Strat.