I found they die pretty easy if you can at least HIT the damn things. They're talented in all unarmed skills, plus observer and dodge, so you'd likely need more than talented skill in your weapon skill, good shield and dodge skills (probably best to have more than skilled), and a shitload of luck to take them on in a fair fight. As it stands, you absolutely must not let them close on you, which means dumping points into agility and removing your backpack-o'-crap when the fight begins to ensure you've got a speed advantage ( > 1000). Engage them one at a time, charge the one you've singled out to knock him down, as long as his buddies are more than 2 tiles from him, and make sure you get a hit in on a leg or foot. You want to get them all prone, to remove their speed advantage and reduce their attacks. This is going to be obsolete in the next version as Toady said on the dev page that he's implementing the attack/movement speed split, so getting them on the ground will only prevent them from catching you too easily, but they'll still flail wildly at you and have a good chance of causing major damage with each swing.
If you take any hits, even bruising, back up and reassess your situation, and preferably spend as much time out of reach as possible. If they knock you over or cause any injury that induces even moderate pain or nausea, it's all over for you. All. Over. If they somehow fail to maul you enough to reduce your speed, take the chance to bugger out and find somewhere to sneak and try to wait out the night and gather your gear.