I’m 68 now with 4 locks and a holy priest.

If you want to focus on PVE, you must have a Pally tank. Voidwalkers do not make good tanks; they do not scale with gear, and get crit often.
Right now, I just manage normal 5 mans. I don’t see this setup doing heroics without a real tank. As luck would have it my irl is a prot pally. I’ll just have to rotate my toons to sit out a run for him to come in. Do yourself a favor now and just make one to roll with the group, you’ll thank me later.