Owen not saving him was a pretty big indicater he otherwise would have died at the crater, and there had been a couple referances to their being another Soul inside of him, the first being Mephilia sensing it.

And Airy's sister was the only reason Tiz was alive. In addition, Tiz is the one who 'returned what he borrowed' as it were. This was pretty obviously going to happen at some point I felt, and something very in-character for Tiz to do. Now, I hadn't considered what would happen, so the death caught me by surprise.

Comparing to Persona isn't entirely fair because a) Persona 3 is simply one of the best games ever written, so I'm not going to hold it to that standard. Lo and b) Tiz was never a heroic sacrifice. He was just some guy who was there and who was willing to do what he could, though he was never really suppose to survive the opening of the crater, so he's more a guy going forward on borrowed time to begin with. The game just never tells you this directly, at least not until the credits.