I believe all of the bigger Steem sites take a 25% cut, Busy, DSound, DTube and DMania (but don't quote me on that, been a while since I read about this stuff).
Due to that there was even talk about making Steemit.com itself take 25% so that 3rd party developers can make a living without people preferring to use Steemit.com just to get out of the 25% cut. I don't know what happened with that idea though, I thought that was a great idea.
Even better, IMHO, make the 25% cut obligatory, so that everyone takes it and nobody tries to create competing services that don't do anything but offer taking a lower cut. I'd much rather have people competing on features and innovation.
Also, 25% might seem high, but the industry standard is a 30% cut for the platform operator as far as I'm aware, so 25% might even be a bit low.