there's not enough cav and infantry in random skirmishes as well
dying to cav is always archer's fault no matter how fast and how silent the cav is, pub players just usually have not enough experience to play around that. And you can't balance game around players with no experience.
There's a huge gap between random skirmish players and competitive players, so big, that most of competitive players can play 100-0 against pubers, and this thread's topic just proves that. The bad thing is, game can't satisfy both competitive players and public newbies simultaneously (actually it hardly satisfies either of them).