Ever consider Xenagos, God of Revels? If you get him out before Scion, he gives haste and pumps Scion into OHKO range with double strike.

I run Xenagos, God of Revels along with Berserk as a way to one hit kill players with Dragon Tyrant or Atarka, World Render

Crux of Fate?

Yes, I should. I haven't played Commander in months and I really need to take a look through all of my decklists again.

Decimate instead of Fumarole?

Yes, that would be better in most situations. Sadly, I haven't shuffled up this deck in more than a year. I think the list is also inaccurate, as I'm pretty sure I remember removing a couple of the cards still given here (and Fumarole might actually be one of them).