Actually Berg, that's exactly what I played. But it's not just the squad, it's how you play it. Any experienced gamer will tell you that.
Honestly, I'd stick with this one:
Darth Vader with swarm tactics-31pts.
You asked about asteroid placement earlier, and with this build, you can be more flexible with where your opponent sets up his asteroids. Generally speaking, Imperial squads want to fly in formation and focus fire. With 6 TIEs and asteroids, that can get a little dicey, especially considering this will be your first tournament. With this build, you can split your squad up into 2 (or more) groups if you desire, and still not lose too much of your effectiveness. You'll still have 2 strong wings of TIEs coming in, and you'll be able to avoid asteroids better. Best advice is to practice some opening maneuvering with asteroids either by yourself or against someone. Try it with one formation and with 2, and see what you learn from that. Have a couple of xwings do their maneuvers as well, so you get a feel for ranges during the second turn, which is generally when combat starts. And you want to keep asteroids out of your way, but you can bet your opponent will be placing his in your way, which is why a 2-wing attack might be better at avoiding them. It's also less predictable, which is more flexibility for you.
And most of all, have fun!