is patent or trademark revocation rare?

It is not very common, but also is not rare. As for the Redskins trademark, it is still in effect until the decision is affirmed on appeal, which appears not to be very likely. Based on the same facts and a similar decsion by the Trademark Office, the District Court reversed and no reason exists to assume that the court won't reverse again (remember the Trademark Office does what the president wants it to do, but that is not the case for the courts).