I got my locks up to 60 recently. I used my hunters as a guide, but I cheated and used 4 locks and 1 priest. I think that will be my new strategy. 5 of one class is FUN as hell, but for instances, it is too nice to have a buffer and a resser.

I wanted some tanks. So for easy content, I just used (pre-50), imp, 2 succy, and felhunter. For harder (easy instances), I used a void (improved talent and glyph), succy (improved talent), imp (improved talent and glyph) and felhunter (with glyph). For super hard (too high level-complicted fights, etc) I used 2 voids, fel, imp. All were demo to get pets and me buffs since I was racing to felguards. Once 50, I used 3 felguards and felhunter. I could pretty much destroy anything. I put stam gear on my 2 locks that would be doing voids and spirit on the rest.

I never cared how much damgae I was doing since if my pets died, I figured I would die. Some fights my pets were too strong, so I had to use wand to start the fight so I could tag the mobs before they killed them. 5 pretty nice blue quest wands with OP pets is so fun. No downtime and no thinking. Then on bosses, being able to load up 3000 DOTs and not worry about pulling aggro (do to voids being stronger) and even if one void died, you got another. I had the talent that lowers the damage done to a health-funneled pet and put my voids (later felguards) on the first push of health funnel and then all pets on second push.

I admit it might get harder in Outland instances, so things might change. Hope that helps. Good luck.