Its hard to separate swords and a lot of times you can't in time.
I just split them in half, they move in rows, if I have one row I select 3 and move them back a bit. It reduces your losses greatly. If you really want to screw bombers up, a wall stops bombers dead in their tracks until they get higher tier units, but a wall isn't going to cut it early game.
To fight Chaos, you have three options, in order of effectiveness (from my experience trying them) they are:
Rage Swords
Sword + Archer
Turtle
Rage swords requires you to micro and seperate, in which one screw up can make you lose the game. I still prefer this, since it is more powerful when spliting properly. The rage swords seperate at the sight of bombers and when the bombers are gone, THEN they activate rage. If you activate rage before the bombers detonate, your swords have lower health and more will be killed by the explosions. After the bombers are gone, I rush their crawlers or miners (depending on what they have) and on short maps, don't worry about the castle dead. One sword to block it or just rush in and garrison when your work is done or whatever.
Sword and Archer comes out quickly and by the time you have sword and archer, they will have 2 bombers, or a crawler with another queuing up. Kite the bombers (since they will inevitably go for the archer) and if you kite well you should be able to take out one, maybe two depending on when you started kiting, but usually one bomber for me. A crawler is even easier, forward kiting and then when they get to their castle, sword could go for crawler (keep it away from archer) while the archer shoots away at the miners. I don't use this often, since I mainly opt for rage swords as the bulk of my anti-Chaos force early game and mid-game.
Now a turtle, I used this twice and failed both times, but I lasted a bit. Ask a turtler for more info, I'm horrible at turtling.