I think a lot of Legends make their way up through getting good at 1 course which is a mistake. I always recommend playing ALL of the courses and finishing your games. I think too many concentrate on their "WGT Average" and unfortunately move up the ranks faster than their ability. Those are sometimes the one's that you see complaining.
The reason you don't see the top Legends complain about "sandbaggers" is because they don't have to worry about credits anymore. Those Legends that are still fighting it out on ready-go's for 100-300 credits a match.... they tend to get a little upset about losing to someone they "feel" should be at a higher tier.
My feeling as I've stated in other forums.... if you think they are sandbagging... don't play them. You can see who you are playing before you play... if you decide to play.. don't complain.
My 2 cents :-)
Cycle