The point is, the overall rating could have been anything. Below average based on these three, but another three cachers may have had even more different opinions on what "cache rating" is supposed to be.
Perhaps the next person along actually hated it, but thought that it could be a good cache for someone just passing by who wanted a quick break so gave it high marks. Then the next one thought the same, but as it didn't suit them marked it low. Then the next one saw who created it, doesn't like that person's caches so marked it low without finding it.
It would probably end up "average" after a lot of finds: so what does that tell me? Nothing, because I don't know what people were judging the cache on.
I would have expected guidelines to let you know how to judge a cache. Whether it's strictly how much enjoyment you got out of it at the time, or whether you're supposed to judge if it's a "good cache" according to the TC definition (which is?). Or whether you should use your own personal definition; or whether you should judge that it's generally good, but not for you. Perhaps you should only mark it if you found it, or perhaps a DNF is sufficient. Should you mark all caches based on trying to encourage or discourage certain types, or is that bad form. And so on!