> The delay of 50-80ms introduced by the network is not terribly much (everything under 110ms is fine for playing Dota)

I don't think you're giving the Dota client enough credit there. Game clients don't wait for network to pretend to respond to user input, because it absolutely is noticeable at 100ms latency. Instead, they predict as much as they can client side and display it as fast as possible. For this reason, the client is not at all thin. It knows how to run the whole program by itself. Not so with remote X11. With remote X programs, the client doesn't know what happens on click for anything, so the user really does get hit with a 100ms delay for every interaction with the program.