No point in spamming Blood boil on 4 targets.
You need at least 4 targets that will live longer than 10s for it be effective. The only time I spam BB is when I have, oh fuck thats a guys pissed off at me.In heroics, HS cleave does more damage unless you literally pull a whole room. Which I have been known to do, but one BB generally works better so I can save other runs for mitigation.