If you have ever been with a group of folks that properly play the dragoon class, you would know that they aren't underpowered.
Spend some time as dragoon, as Russian ones (we played russian anyways), they have the cavalry muskets, granted.
They are then basicly light infantry with an ability to be somewhere fast, very fast.
I also experienced proper dragoons as enemy, and sweet jesus that single dragoon company was fucking everywhere.
It is true that dragoons barely pack a punch when used as hussars: they aren't fast enough. But they work just as well against rifles and artillery as any other cavalry class.
It's just incredibly stupid to use them as tank cavalry. They aren't made for it.