Yesterday, we made a change to how our rate limits affect OAuth applications. The 10 requests per second limit that we mention in our API usage guidelines will also be applied to any requests made by apps using OAuth (both OAuth1 and OAuth 2.0).
For OAuth apps, the limit will be applied per portal, so any requests made for a specific portal will be limited to 10 requests per second. Your app will be able to go above 10 requests per second total across multiple portals.
Sorry for the late notice on this. If your app is having problems with the limit please let us know here.