I can't figure out this guy's build.
poe.ninja
I mean, I get the intent. Curse shit, end the hex somehow, high level doom blast triggers and causes a high damage ignite. With Shaper of Flame, Profane Bloom, and Fan the Flames, that more or less proliferates as far as Fan the Flames and Profane Bloom will reach almost instantaneously. This is standard Elementalist stuff for a while with Obliteration wand, new to Occultist as of this patch.
What I can't figure out is how he's ending the hex with doom early. He's got enough duration and temp chains that it lasts at least 20s. Is it because he's under the curse limit and the last curse triggered by Vixen's ends Despair almost instantly? If so, that would make for some shitty single target dps since it will never have any doom. I guess you could somehow swap in +1 curses for bosses. But even then, you don't want for the curse to end naturally. Does casting the same curse again count as ending it for Impending Doom?
Finally got around to testing it myself.
Self cast 1 curse supported by Impending Doom: will never trigger Doom Blast by casting the same curse again. You have to remove it via Hexblast or letting it expire naturally.
Self cast 1 curse supported by Impending Doom and trigger 1 curse in Vixen's Entrapment(+1 curse limit): pretty much the same thing.
Self cast 1 curse supported by Impending Doom and trigger 2 curses in Vixen's Entrapment: self cast curse goes boom. Impending Doom seems to be scaled by Doom on self cast curse because spamming it was definitely resulting in less damage per hit than waiting for a few seconds.
This seems like a bug? Sure, you're not cheating some 1-2 combo down to one button as you need to curse a pack and then curse it again. But with Profane Bloom, the proliferation available to ignites, and base cast time on curses, you're likely still cruising along quite quickly and comfortably.