I'm afraid not.
Several times, decent snipers have been told to switch away because of the listed reason.
Let's run over some of the things that make the sniper awesome in MvM:

JARATE!
It's a jar of pee, and it makes robots lose hope of their life, if they even had emotions. Not only can you throw it on a large group of robots to make them vulnerable, if you upgrade it, you can slow them down too! This makes super scouts MUCH less scary.

EXPLOSIVE HEADSHOT!
Imagine this, you have no soldiers, no demos, but instead a sniper, you're getting gangraped by a bunch of scouts, when suddenly, a headshot flies from the blue and all of the scouts die at the same time.
The explosive headshot is just that; when you get a headshot, the surrounding robots are hit and take bleed damage. which makes the sniper great for crowd control, and a GOD at taking out medics.

MASSIVE DAMAGE!
A maximum upgraded sniper rifle can do up to 900+ damage in a single headshot. combine this with explosive headshots and you have a giantkiller.

RED MONEY!
Red money falls out of robots when you kill them with a headshot. What makes red money so special? it is automatically collected when it would normally expire. need i say more?

The Sniper loadout of MvM is VERY strict. If you don't have a thing right, you're going to be crucified, probably kicked, too.
It should like something like mine:
(Warning: Outdated picture. Not the loadout i use.)
So what are the good weapons? let me run over each weapon.

PRIMARY

Sniper Rifle + Reskins
Use it if you don't have anything else. There are definitely better ones, but stock is the all-around best in most situations. Just not MvM.

The Machina
Best Rifle for MvM
YES. YES. A MILLION TIMES YES. This is the only weapon in the WHOLE GAME (Besides backstabs) that can do 4-digit damage to giants. MEANING 1000+ DAMAGE HEADSHOTS! You don't even have to spend any money on projectile penetrations!

The Hitman's Heatmaker
Second-Best Rifle for MvM
The community favorite, but i don't quite buy it. If you're not keen on re-aiming when you re-scope, go ahead and use it. But there are just better alternatives in my opinion.

Bazaar Bargain
If you have none of the other rifles, use this. It's better than the stock, since you should be getting headshots all the time. And if you don't... well, why are you even playing sniper?

The Classic
-No headshots unless fully charged
Need i say more?

The Sydney Sleeper
Third-Best Rifle for MvM
Little known fact about this weapon! Even though you don't get headshot crits, it still can deal explosive headshot damage to surrounding enemies! You're trading away your headshot damage, the defining feature of the sniper, but also applying mini-crits to whatever you're shooting at. From a safe distance, as well! Unlike the scout that needs to get right up close with his Fan, you have a mobile pee-shooter.

The Huntsman
Not only do you have a really vague idea of wether or not you'll get a headshot, there is one glaring problem.
EXPLOSIVE HEADSHOT > BLEED DAMAGE

SECONDARY

JARATE
YES! Minicrits for all your teammates! Slowdown on enemies! A lifesaver! USE IT NO MATTER WHAT!

EVERYTHING ELSE
Switch to another class.

MELEE

Kukri
No special stats, so nothing to worry about. you shouldn't worry about your melee anyway, except for tank waves.

Tribalman's Shiv
Lower damage, but it can inflict bleed. use if you want, but the tank dosen't take bleed damage.

Bushwacka
Prooobably the best. You take more damage while it's out, but you get a buff banner soldier, you can just thwack away at the tank.

Shahansha
Use it if you want, lower damage unless you're injured. the thing is, you'll most likely be fully healed on tank waves. and a medic can ruin that damage bonus for you, plus, do you want to run around with 60 health just for the damage bonus? Thought not.

REQUIREMENTS
Explosive Headshot (350 Credits apiece, 3 Levels.)
Jarate: -35% Speed on Target (200 Credits, 1 Level.)

RECCOMENDATIONS
Primary: 25% Faster Charge (200 Credits apiece, 4 Levels.)
Primary: Projectile Penetration (400 Credits, 1 Level.)
Jarate: 15% Faster Recharge (250 Credits apiece, 4 Levels.)
Primary: +25 Health on Kill (200 Credits apieve, 4 Levels.)

OPTIONAL
Primary: +25% Damage (400 Credits apiece, 4 Levels)
Primary: +20% Faster Reload Speed (250 Credits apiece, 3 Levels)
Melee: +10% Attack Speed (200 Credits apiece, 4 Levels)

EVERYTHING ELSE
Who am i to judge? buy whatever else you like. if you have the cash.

Achievement Unlocked: Alliteration, ♥♥♥♥♥♥♥!
Seriously though, i got quite a bit of people asking about the sniper strategy, what insight can i bring you? here are some examples.
QUICKSCOPES VS. HARDSCOPES
Quickscoping? That's where you scope, shoot, scope, shoot, scope, shoot. It's quite effective if you're a good sniper, that being said, it works wonders on groups of scouts or other weak classes. Especially with the Explosive Headshot. The downside is that the pyro is the straw that breaks the camel's back, or in this case, the 175 health that breaks the 150 crit.
PROS
Fast and Efficient.
Great on low-health classes.
Chaining them together does wonders.

CONS
150 Damage.
Can't kill a pyro in 1 hit.
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Hardscopes? That's where you scope and charge before you headshot, quite useful on giants. and if you upgrade the charge time, you can essentially turn a Hardscope into a Quickscope.
PROS
High Damage
Great for assaulting Giants.
Devastating explosive headshot.

CONS
Takes way too long.
If you miss, you need to charge again.
Upgrade needed for maximum potential.
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Noscopes? Please don't. I only noscope when i'm running towards a tank.
____________________________________________

HIDING SPOT VS. OPEN AREA
Want to get a hiding spot? It may take some time to get a good spot, but if you can find one where you get a lot of cover, go for it, just keep in mind that bots aren't humans, they will notice you if you're hiding.
PROS
Less damage towards yourself.
Away from the action, more complimentary to hardscoping.

CONS
Away from the action, can't assist teammates as well.
Bots will detect you.
Throwing jarate and hitting something is more luck-based.
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Want to go out in the open? You're going to take more damage, but you'll get more of a clear view of the action.
PROS
Closer to the action, so throwing your jarate isn't luck-based.
Clearer view.

CONS
You're out in the open. you're going to get hit a lot.

Every time I join a game, I usually see idiotic snipers. So here's a guide on how NOT to be an idiot.

HOW NOT TO BE AN IDIOT: THE GUIDE: THE MOVIE: THE GAME
Don't use the Huntsman, Razorback/Cozy Camper, and Bushwacka.
Don't go sniper when there's 1 or 2 already.
Don't argue with the team. If they all agree that you shouldn't go sniper, switch away, if everyone agrees except for the new guy with the bad loadout, stay sniper. If they tell you to switch loadouts, you listen. If everyone is fine with your current one except the gibusvision huntsman sniper, keep it.
Use the jarate, and get the slowdown.
Don't choke up.
Don't run into Intermediate, Advanced, and Expert difficulties without experience, start training in Normal first.
AND MOST IMPORTANTLY.
If you never land headshots, DON'T PLAY SNIPER.

I suppose so. Until you decide to call me an idiot for not going over a super-specific thing, and then post that in the comments, there's nothing more i can add to the guide, i'll work on it as i get more experience.