I would totally agree with you that there is more to an epic fight than odds, and that those things (evocative descriptions, imagination, etc.) are critical, but surely seeing that the odds are against you and yet somehow pulling it off makes it that more fun, right?
As a player, I try not to assume that I have a good estimate of the odds, to be honest.
In the encounter (which wasn't D&D, but I don't think that matters much), the players first thought it was going to be pretty easy - they thought the guys was a mad scientist, and they disguised themselves to get on his airship and had six to one odds. Their only real fear was that he had some massively dangerous weapon.
When he jumped out of the airship, fell sixty feet, and got up and started to run away, they got rather more scared.
When they figured out he was undead, rather than mechanically enhanced, they got even more scared.
But, the actual difficulty didn't rise. He didn't have too many ways to hurt them on hand. And, in fact, learning he was undead also gave them the information on how to kill him - they got more scared, but their chances of permanently beat him skyrocketed!
So, no, I'm not at all sure that the chances of winning (either real or perceived) makes the thing more or less fun. A grinding combat is a grinding combat, no matter which way the odds are.