As a person that has open carried for 43 years, I have never had anyone attempt to disarm me. I have had shady people cross the street to keep from walking past me though, and one open assault stop short (the guy was screaming he was going to pound me into a pulp). When the guy saw I was armed (carry never left the holster) he changed his mind very quickly, and left.
IMHO, a LEO is much more likely to be put in the position of an attempted gun grab than a non-LEO. That does not mean you do not need to know how to defend against a gun grab, just that when you Open Carry you are telling everyone that you take your personal safety seriously, and most likely will know how to use what you carry. To my knowledge no one, other than LE, has every had their OC successfully grabbed and used against them.
A LEO, on the other hand, will insert him/herself into a situation where the person being arrested, detained, etc. may panic and not do what that same person normally would in the same situation with a non-LEO. Panic does strange things to people's ability to think rationally.