I seriously doubt you're going to do a better job at security than the AaaS systems out there. I couldn't, and no-one I know could. It's a ludicrously complex and subtle field.
How did you evaluate the auth implementations? In my experience it's about as hard to poke holes into something as it is to fix it. Besides, a custom auth implementation doesn't need to be best-in-class, it needs to just be good enough.