Aslong as the priest is just there to be a pocketed healer...such as not do anything but heal then yeh I guess its an ok build.

The more warlocks you roll however, the less the cooldown will be on your soulstone for your priest. Soulstone your priest, then your priest can res your whole party. At level 70 or so if you spec deep holy and get circle of healing, this is an instant cast spell that heals everyone in the targetted persons group which SRSLY owns...until you get that high, there is always Prayer Of Healing or Holy Nova to AOE heal with

And with warlocks, your life is your mana, so if you have a priest then UNLIMITEDMANAPLXKTHXBAI. Which means unlimited pulls..which means you can kill whole zones of shit before it starts respawning.

Downside is, you are all squishy and you lose 1 dps but you have survivability providing in PvE you keep enough threat up on your Voidwalkers and in PvP make the priest stop follow about 20 yds from your locks otherwise people will rape it.

You have a long way to 70 though!