Four locks are overkill, do it for the badges when you can, summon another toon in to tank when needed and kick it out when your done.

I find the slsl build easy to quickly get the four locks their amp'ed out and trinketed dots up I have one lock that goes heavier into demonology to get a the felguard and he health funnels rather than drain life. This gives you very quick turnover and very fast kills. Your primarily using the priest to keep the locks tapped up and tossing direct heals at the pets casually. No issue with threat.

Also having the raid gear for the 10% damage -> health helps.