It's hard to say whether or not RWBY is on topic for the site by definition alone. The series itself is very derivative of anime culture, but it stands out on it's own as a genre... in the West at least.
If anything I think we should count it like a self-published work similar to doujinshi works from Japan. Now I'm not saying or claiming RWBY is doujinshi (a self-published work). While it's unique on it's own being the first published web series of it's kind by an American production company, it like the many forms of self-made doujinshi content from Japan, RWBY was made and developed by fans of the subculture just like Touhou and Vocaloid developed in Japan.
We mustn't necessarily dismiss RWBY or works like it as "not anime" simply because it's not from Japan. Sure, in a purely technical sense RWBY is not anime because it doesn't come from Japan. This doesn't mean that it can't become a part of the subculture because it's not from Japan. The subculture has become what it is today not solely, because of Japan (although it is responsible from much of the content) fans from all over the world have made anime what it is today by talking, sharing, parodying, and creating their own content. Some do it by emulation, while others use it for inspiration. It's thanks to the fans anime has become what it is today. Much like sports, it'll never get anywhere without it fans.
RWBY may see cheesy and "unanime-like" at first, but people worked hard on it -- let it grow and develop, perfection is an art yet to be mastered by people. We're already in agreement that doujinshi is on-topic for this site. So instead of arguing whether or not it's anime in a technical sense, why not give RWBY a chance and see if it belongs in the culture? If it's something we like we can keep it, if it's not what we wanted we can shelve it. Don't just think about anime and manga just by where it's from or who it's by, think about anime and manga as a culture. While opinions may vary, it the voice of the community as a whole that determines it's culture.
tl;dr Let's see RWBY for the culture it represents not where it's from and see how it goes from there.