[2.0] The Divine Pyromaniac, a Righteous Fire and Incinerate build

Why don't you drop the life/mana regen cluster and get a bunch more jewel sockets?
You're not taking Marauder, Duelist, Templar and the one between Marauder and Duelist at 2 points each.

Btw, at gem level 20, your Incinerate will cost 1-2 mana per cast.
You need additional mana cost reduction then, even with -8 x3.
(one of your jewels has reduced cost, but you're also wearing a -7 elreon, so this will still not be enough)