I've had good success just throwing up raids online with random players when my usual group is not on. IMO, the main problem is that most of the AI are glass cannons who go down in one or two hits. A sandstorm pretty much guarantees a wipe on 5 star max with AI. Almost any human player will do better... unless they bring type disadvantaged glass cannons, in which case they're at best on par with the AI. Even then, if they understand they can heal they still do better. In my experience, three fourths of randoms know what they are doing, and the last fourth either do not really have the Pokemon to do the raid they joined or just want to use their pet favorite at all times.
In my experience, one decent random joining is enough to clear most five star raids. No friends really needed.
In my experience, one decent random joining is enough to clear most five star raids. No friends really needed.