It only took like 500 attempts and several weeks (yes, weeks...ALL of my luck went into getting that Aurora Peacock), but I FINALLY got Dark Sabertooth!
It's mostly a big deal because she has the potential to be another pet for the same amount of time and there's no way to manipulate it so 12 hours guarantees that you got her, so it's a 12 hour coin toss (with the set up, it's possible to get Flower Frillzard as well). With her gotten, I can finally complete Quest set 3 and start focusing on the other pets I need to summon.
Only Surfur Penguin, Swamp Crocodile, Thunderball Puffer, Matador Flamingo, Whirlwind Hawk, Dandelion Meerkat, and Universe Dragon remain. Getting closer to getting them all! (Not including Limited pets or Cafe of Secret Pets)