questions about optimal Blood Boil warlock build

So far I'm level 75 and have 1 point in every Demon skill except consume. Maxxed Blood Boil and its 2 synergies. I have +7 skills from my gear and 3 hard points in Demonic Mastery so I can summon 2 demons. What do I focus on next? Do I max Demonic Mastery, Bind Demon, or pump points into Defiler or Tainted? I'm at a loss. Also I assume 1 point into Sigil: Lethargy is worth it for bosses? And do I bother with Consume?