No, villains have not become too scary. Villains in movies, books and TV shows are supposed to be scary. That's their whole purpose in the story. Furthermore, Batman is not necessarily a children's story, so it's okay if the villains are too scary for children, since the story wasn't necessarily meant for them.
No I do not feel that movie villans have become too scary. Movies are made for entertainment purposes; comic book movies are made to mirror their comic counterparts. It is unfair to say that movie villans are "too scary."The phrase "too scary" is subjective in nature. If people feel that an image or situation is too scary they have to option to refrain from viewing it.
No, villains have always had the primary function of inducing dread and a strong repulsion in the audience. Someone to fear and hate. It is only natural that modern villains follow the trends of the day to achieve that effect. Frankenstein's monster, Dracula and the Mummy were terrifying in the past; now they are goofy cartoon characters used to sell candy on Halloween.
I believe that villians have always been as scary as they used to be. The world has just become a lot more sensitive to every little thing going on around. All villians are simply set at the level of how sinister each movie or show is. Perhaps, films get more scary, but the villians are only on the same level.