i find that it's fairly hard to manage the healer in pvp. With priest + 4 warlocks anyway. What usually ends up happening is the priest gets focused - so in a equal numbers encounter what this does allow you to do is free cast with the locks and blow up several people while your priest is dying. In something like AV is this less useful. Certainly having a pocket healer is useful - it's just hard to play nearly as efficiently as say, another lock, or other 'spam this button, watch something die' class.