I had the honour to play against Warhuryeah's cow mangler, where he mostly used the mouse2 option of the weapon. I know it has downsides (losing all of your clip, being forced to charge, moving really slow) but still it can give the option to instagib anyone except a soldier. I think even a medic will die to the burn afterwards and in midfights the Demo doesn't usually have full hp. Just a cheap way to get kills and not fun to play against. In gullywash we lost 3 mids because either our demo or medic died instantly. In badlands, maybe two mids.
I know that eventually people will realize how to counter it, listening to the sound and being more aware where the soldier carrying it is. But for the moment, it's super annoying to play against.
Not to mention if you don't like using the mouse2 shot, you can always rely on your primary fire which is basically identical to normal RL but has 5 rockets and no ammo. Not being able to get kritzed and doing shit damage to sentries are not significant downsides. Also the projectile feels like being harder to dodge. I'm not sure when the projectile actually hits and what is the radius etc... Maybe it's just me.
On the other hand I think soldier needs a buff as it might be a bit weaker than demo at the moment. Nerfing the scout would be a better way to buff soldier imo.