Torrential Gearhulk doesn't have enough instants to target in this build, and will probably become Noxious for removal. The removal and life gain aspects of Noxious are huge tempo swings against the aggro decks and menace helps close out games quickly after using your sweepers to chew up the little blockers. Scarab God eats other recurring threats your opponents will have, and also adds to your board if you need to go wider, or put up a wall that filters your draws and drains your opponent for a bit of reach to finish games. Saheeli overperformed for me in a midrange/control heavy environment, sneaking in under a bit of countermagic in several matches where my opponents were still trying to fix their mana, setting up my draws for the next several turns and giving me access to hasty attackers and an ult that can win the game almost on the spot. I'd recommend adding a second copy of her to your board for sure, possibly a third. Glimmer seems like a suboptimal sideboard card, and is probably for the midrange and control matches, but a great card in the mirror matches is Dispossess. Again, for three mana you get access to a card that can heavily swing matches in your favor by proactively stealing their Gearhulks, Walking Ballista, or Dynavolt Towers. This allows you to save your countermagic for their non-creature threats and removal targeting your threats. Since Hour of Devastation kills all your main deck creatures, you might want to swap those to the board and start the Curators for more cheap, evasive threats. Archfiend seems strictly better than the Granitic Titans also. Oracle's Vault seems too slow and often ends up exiling something out of your means of casting. Chandra, Torch of Defiance will still do this on occasion, but gives you other options to help accelerate your board or remove a pesky creature and her ult kills very quickly.
In summary, main deck: -2 Hour of Devastation, -2 Oracle's Vault, -4 Granitic Titan, -2 Disallow, +2 Chandra, Torch of Defiance, +2 Curator of Mysteries, +4 Archfiend of Ifnir, +2 Supreme Will
Sideboard: -3 Glimmer of Genius, -2 Torrential Gearhulk, -2 Curator of Mysteries, -2 Archfiend of Ifnir, +2 Noxious Gearhulk, +2 Scarab God, +2 Dispossess, +1 Saheeli Rai, +1 Dispel to help win counter wars and protect your dudes from instant removal
The last slot can be a third Archfiend, Glorybringer, Sweltering Suns, or Saheeli, a second Dispel, or a 1-of Chandra Flamecaller which can act as another sweeper, filter, and win condition all in one. Let me know what changes you settle on and how they do for you, as I plan on revisiting a shell similar to this myself.
EDIT: Since it seems blue is more of your splash color, I swapped the Archfiend and Curator numbers, and dropped Disallow for Supreme Will. You can still counter anything early on, and Impulse later in the game when the Mana Leak mode is worthless.