That sounds like it would be incredibly useful in a game with encounters that aren't as perfectly scripted as this one. Also, even if you don't time Hallowed, you still get use out of it because it negates all damage and prevents you from getting vuln debuffs. You don't have to wait to reach 1 hp for it to start working.

You know, if you're really that keen on Living Dead, I'd happily trade you for Hallowed on DRK.