I also disagree with the main points. A lot of it seems to stem from not having a good idea of what they are and aren't going to be doing with this matchmaking. A lot of it is also based on past experiences with crappy matchmaking system which Blizzard's setup seems to be a far cry from. Lastly, you're lumping 'community' into a ranked tournament setup. Shamus, you aren't looking for a ranked tournament arena, you're looking for a casual arena. On one hand, you have open games, a possible soft-LAN setup, and whatever clan/friend's list systems they decide to implement. These, along with external communities, will all let you foster the game community you want. Make an open game, invite the people you want to invite, and tada!
One the other hand, Blizzard's proposed system will let ranked matches be much more meaningful. The idea behind it also stems from the one behind the random dungeon system they implemented in World of Warcraft. Yeah, it hurt general community quite a bit, but on the other hand, people didn't have to dig around for over an hour just to find a damn tank for the damn daily heroic dungeon quest. It improved the game, but meant that players had to do the community thing themselves. It's kind of our own fault when the community aspect there suffered. I mean, it's an MMORPG, how many more guild opportunities, chat channels, world events, and general options for community do we need?
So with Battle.net and Starcraft 2, they know the kind of tools we want, and I'm sure that most will get in there sooner or later. That, and there's a good chance that whatever ranked bracket you end up in will foster that old sense of server you had with Unreal Tournament. If someone moves out of your bracket, you will have the friend's list to back you up. Also realize that when someone does get good enough to curb stomp whatever community they're in, even if you are all good friends, it's typically hard to play competitively with them and still enjoy the experience. There are points where those people need to move on or quit the game because that competitive spark is lost for them and no one wants to play against them. In the ranked brackets, they'll move up, and new blood will be brought into your bracket/community.
Lastly, I think there are aspects of FPS matchmaking and RTS matchmaking that only make a loose correlation to each other because of the very different way the two types of games typically play out. Your comparison and expectations from the one to the other may be flawed.