Here's why I think 1984 was the most painful of the four:
John Elway in his 2nd year really took charge of the team (after some weird rookie experiences). Lotsa you guys are too young to recall, but a 23-year old John Elway on the Broncos, universal #1 pick, that was a "morning in america" moment. The team's future was so bright, never brighter. Went 13-3 with relative ease. 9-7 Steelers came into Mile High, nobody gave it a second thought ... a lot like the 96 Jags in that respect.
Here's the kicker: Opponent for the AFC Ch-ship game the next week? All set to have been the 14-2 Miami Dolphins, and their stats-happy 2nd year QB Dan Marino. Yup, the Orange Crush was already packed for the Orange Bowl when this one happened.
The Elway-Marino matchup was more anticipated than Manning-Peyton, it really was. Plus John had real problems dealing with Marino's stats explosion, it bothered him more than anything. It was the genesis of the Elway vs. Reeves feud really, in that John (and 1st yr QB coach Mike) started thinking Reeves was too conservative (wasn't true, Broncos threw the ball as much or more often than any team).