I have two warlock boxing groups.
Team A - 5x SL/SL Warlocks, lvl 70 in S1 PvP gear.
Team B - 4x Affliction Warlocks, lvl 64 in quest/crafted greens and blues. 1x CoH Priest lvl 70 (crafted and some 10-man gear).

Team A was used mostly for non-arena PvP. Team B is supposed to be a grind/farm group to finance my priest. Its quite a challenge to do instances with just 5 locks and no healers. It is an exercise in micro management since voidtank and spank only gets you so far, even on the trash. I've been doing more instances on Team B and having the healer does make things smoother without a noticable drop in overall DPS. Team B has done ramparts, blood furnace, slave pens (except last boss) so far. Team A has done ramparts, blood furance, and underbog when they were the same level.

Threat generation becomes the biggest issue after the healing is sorted out. Our pets don't have a true 'taunt'. On some bosses I would have to wait until the voids were OOM before unloading. Using PoM every cooldown to help them generate more threat. On bosses where the voids take a lot of damage, you will find that your healer will pull aggro before the tanks becomes unhealable. Felguards might help the situation a little.

Once Team B is 70, I'm going to regroup Team A with my T6 holy priest and try out more instances. I'm not interested in decking out any of my warlocks with badge gear so don't mind the fact that they are a weak heroic group. If you wan't badge gear, roll shammies or make a tank/healer/dps team. Warlocks for a PvP face melting team that brings out the QQ in your opponents.

Maybe blizzard will buff the pets in the future.