Death is one consequence that can be caused by a vast number of effects in the game. A death you could not reasonably have foreseen is never a positive thing, but it's tempered considerably by the fact that you can do the same thing right back at them. A long respawn sets you back farther, but it lends a certain rhythm to the game. For all that the die-respawn cycle takes control out of your hands, it is also normal. Killing and dying and coming back is a part of the context in which the entire genre is played, it's the one mechanic most central to the design of the game, and while respawning might not be objectively preferable to being stunned, there's a lot to be said for familiarity and reciprocity.
So stun feels more out of place to you because you are not used to being stunned. From an objective standpoint the stun and the death are equally normal, and your aversion is preferential. Which is what I thought to begin with. Again though, I consider being stunned a much more active experience than being killed. If you get stunned, and just throw your hands up, willing the scout to just get it over with, well that's your problem, and you'd be more successful if you instead used that time to get ready for the stun wearing off.
Stuns challenge that long-standing and well-polished paradigm of play, and they disrupt the continuity of the gameplay. Having control taken away by a means entirely outside the balanced mechanic that dominates everything else will never feel right until it has been brought closer to the core of the mechanics. It's just tacked-on. Only one class can cause this effect, there's no counter to it that isn't also a counter to literally everything else, it's one of two things (the other being knockback) in the game that can't be prevented under any circumstances (reflecting a baseball with a compression blast is a fucking joke, on par with a taunt kill), and its drawbacks make no sense in the context of the established mechanics or even of its own core mechanic and are of no consolation to the target.
Only one class can instantly kill any other simply by means of a melee attack from behind. Until this mechanic is brought more in line with
everything else it will never feel right. This cannot be countered by anything that doesn't counter literally everything else in the game.
Your other point here seems to be that it is different from what can already be done, and is therefore bad. I believe this to be incorrect. The whole point of the class patches is to give each class an alternative method of play and set of tactics, and to further separate them from every other class.
And on top of that, you're forced to endure six seconds of watching the enemy get free hits on you. And that enemy is the one designed to be the most annoying, and the only class that doesn't outgun it in normal circumstances is the one least likely to be affected by the weapon.
First of all, you pulled that number out of your ass. Six seconds is a max range stun, and maybe not even that, and in that case the scout can barely reach you before it wears off. Second, the scout "outguns" damn near every class in the game. A short range to point blank scattergun shot does around 125 damage, non-crit. The FAN does around 100 damage per shot at the same range (this is tempered somewhat by the knockback on the first shot). That's why the damage reduction while stunned was necessary. Finally, no class is designed to be "most annoying". You find the scout to be the most annoying class, while I personally dislike the demoman much more, and others really hate getting sniped.
What does it add to the game, besides annoyance that doesn't really seem to fit? Is the option to rarely and temporarily remove one target from the fight really worth all the rest of that?
It adds the ability for a scout to play a meaningful role on the red team in a defense based map, setting up attackers to be finished off by team mates, and disrupting pushes, or in the defense of or offense of a position on a symmetrical map by doing the same thing.
Also: dodging them?
Yes, dodging them. You don't dodge the projectile when it's already in the air, you begin to dodge before it ever leaves the opponent. The ball has flight time, and the scout only gets one shot. Most scouts will take the first shot they think will hit, and most of them miss me. It's not that easy to hit someone with it when they're shooting back and actively evading.
They go faster than the critrockets you seem to hate so much, never have other attacks of their kind as a warning, and are fired by the class that's hardest to read. Killing the scout first? It's one of two weapons that gets more effective at longer range, so they can easily stun you at a range that you're ineffective against them. Cry some more? That's what I'm doing.
I don't hate crit rockets, and I'm not sure where you got that from my post. If you don't have warning, that's called an ambush, which is what scouts do. Yes, scouts are hard to read, depending on the scout, but all that dodging around screws up their aim too, and the scout only has 125 hitpoints, even if you can't kill them you can often run them off to find a health pack, and if the ball misses you've got a lot of time to do so.
I don't use the Sandman except when the situation demands it anymore, because instead of stunning someone and doing half damage, I'd rather just kill them with my high speed ambushes, and powerful gun, and I see more and more of what I would call good scouts doing the same thing