When approaching him, a lot of Jade Brotherhood and Am Fah will appear and start to fight. They're not hard to defeat, but make sure not to get ganged up on. You can also let the Jade Brotherhood charge Xuekao's position and let them take care of the Am Fah guarding him. Make sure that you kill the first group of archers, though, or they won't be able to take down all of Xuekao's Am Fah guards. Xuekao will be able to kill any surviving Jade Brotherhood, thus leaving himself alone and somewhat easier to kill.
This boss has a very small chance of having Golden Phoenix Strike hit, since he has no long lasting enchantments. This also means that he will most likely never get to use Repeating Strike.
Be careful if you are the first to approach this boss, as his Unsuspecting Strike can deal a terrific amount of damage in a single hit.
The aforementioned flaw in his build is because Xuekao used to have Way of the Empty Palm. The 5/19/2006 update changed his elite skill to Assassin's Promise. However, the rest of his skillset was designed to be used with Way of the Empty Palm. This build flaw is probably related to that of Ilidus of the Empty Palm, who has Way of the Empty Palm, but whose build appears to be based on Assassin's Promise.