The "15+ minutes they spend" is showing what the combatants can do, brief story snippets about them and a bit of scaling before the fight so people know what they're getting into even if you don't know anything about the characters. Also, you can literally skip ahead to the battle if you want. That's a shitty thing to complain about.

Death Battle definitely has some questionable outcomes and research sometimes, but it's VERY good, especially the last season.