Eh, they could've made them worse. They were their scariest in their first episode. But, all they did then was boop people on the back. In their next appearance, they actually killed people, but the setting made it hard to take them as seriously.
Now, the Vashta Nerada were pretty creepy. They would've been creepier if they didn't remind me of Scooby Doo.
But, I'm talking about the older episodes, from the sixties and seventies.