Priest of Forgotten Gods is VERY good, if you untap with it. I playtested this deck once and I got the nut draw of supplier into priest into another supplier + rally on turn three for the kill. While it won't happen every game, Priest of Forgotten Gods's extra mana speeding up the deck's kill by a whole turn was very impressive. Pretty sure t3 is the fastest reliable kill possible in pioneer. And it's a budget deck!

actually i did a search and this is very close to the top tier build of aristocrats rn: https://www.mtggoldfish.com/deck/2987937#paper notice how that list isn't even playing removal in the main, which i think is smart considering how fast a kill you get anyway. maybe you can cut the Fatal Pushes for additional sacrifice fodder like Hunted Witness.

Thanks for the upvote and feedback -Arcanity-.

Priest has been working wonders for me in standard. One tap from her and it's usually game so she's now a staple in the deck.

Interesting point about that other deck. I'd not seen that. Some great cards I've not considered like Fiend Artisan and Return to the Ranks (arguably better than Immortal Servitude?). I'll be adding these in as other options.

I'm still in two minds about Fatal Push. Hushbringer for example can grind our plans to a halt so a bit of a backup plan until we can get back on our feet can be useful. I've also been in situations where a priest activation only results in the opponent only having to sac a low value token rather than something more vital. But if the deck is as fast as you say, I might up the sac fodder count.