Slightly off-topic here, reading this gave me ideas on how to use immolation, though I don't think I will.
Completely on-topic, Immolation with lava golem sounds powerful, but it's like my fire spirits I abuse so much. They get to ridiculous levels of power AND...will be killed by grav pull, drain life, fire bolt, ice bolt, any infection, RoF, scarabs, otyugh, lightning, shockwave, My fire shield being stolen, in addition to being royally destroyed in power by freeze, ice shield, procrastination, petrification, arctic squid, lobotomizer/mind flayer, etc.
Lava golem is the same way, if you act on it early enough. And it is vulnerable to the same things Fire Spirit is. I may be persuaded if you can tell me another reason Immo is overpowered, but if it's just because they can get out lava golem early, I say no nerf.