Yeah Skirmishers are a pain, tankwise anyway, that one gets the Skull every time, then the warrior then the watcher, as soon as the watcher is down prepare for the next set (3 in total) if you kill the watcher first then the next watcher comes into the fray so better off to kill em last in ur group of 3. also when the first watcher is down don't taunt the next group wait for them to come to you. I have a couple of times tried to second guess wich watcher is coming next and got it wrong, then you end up with 2 skirmers, 2 warriors and 2 watchers at the same time.

Hope that is usefull and good luck :P