Are the rats in 5e over powered? [closed]

So killer rat swarms in D&D always seemed weirdly overpowered to me. In 5e a swarm of rats does 2d6 damage, or the equivalent of being hit by someone swinging a greatsword every six seconds. Or enough to kill an average commoner in 3 seconds. That just never seemed right to me.

So assuming they were magically compelled to attack people or something like that would a swarm of regular rats realistically be that much of a threat to a group of healthy humans trying to wade through them?

My instinct is that they’ve be more of a slow and painful environmental hazard than something immediately lethal (dying later of disease or blood loss is a different story).