I SAW HENTAI IN THE THREAD TITLE AND I CAME IMMEDIATELY. Since this thread is appropriately titled we have to talk about it now.
Most hentai anime I come across don't have oversized tits, not today at least. It's mostly pedoy shit. Big boobs and tentacle monsters were big in the 90s, most of the hentai that comes out are like relationshipy oh-no-i-tripped-and-my-hand-landed-on-her-boob stuff involving high schoolers or something. Look up recent hentai anime releases, rarely any of them have ridiculous "jesus enough already" size boobs. I've seen plenty proportionally correct hentai. Manga and doujinshi shit are mixed and always have been. They consist of anything really, whatever you're into.
People don't look at hentai for originality.
Hentai isn't any weirder than normal porn.
We already had this discussion, but I forgot to add some points.
Vanilla Hentai isn't any weirder than normal porn.
But Hentai has a lot more genres that are either mainly Japanese fetishes or impossible in the normal world
EDIT: there is no norm for hentai, it depends on the genre and the artist