Well - I did the only test I could really think of to prove out whether this is a problem caused by this 75gr bullet or just this lot of ammo. I'm now comfortable it's this lot of ammo. This makes me happy because I've previously had good luck with this bullet.
I bought another lot of the same ammo and ran it back to back with the lot I already have. If it was the bullet - then both would have had issues. If it was the lot of ammo, then I'd have zero issues with one lot and issues with the lot I currently have.
Photo evidence below - you can see all three rounds of the suspect ammo have blown primers (three rounds above the box on the left). The three from the new lot have normal looking dented primers (three rounds above the box on the right). Visually, the primers on the suspect lot are silver, while the primers on the new lot are gold. My guess now is it's the primers used on this lot.
Passed this along to the folks at Hornady - will update once I hear back.