Originally Posted by
Kolvarg
1) A boss fight is usually around 10 minutes or less, while a M+ dungeon is usually around 30 minutes or more.
2) In a boss fight you get to try again as many times as you want. You don't have to go get a new key, or to upgrade a different key. Trash doesn't respawn. Usually you even re-spawn closer to the boss you are at. You just come back again and give it another try.
Just because they are both time-related mechanisms, it does not mean that they play the same, and it certainly does not mean they feel the same way to the player.
Like I've said before, I guarantee you the average raider would loathe a 30-minute+ boss fight, even more so if it had an enrage timer.
Or, imagine if after wiping on a Mythic raid boss, you'd have to go kill all that raid's bosses in Heroic again, before being able to try the Mythic difficulty again. To me, that's how out of place the timer feels in WoW.