As Xin Zhao, I find that the best Dominion build revolves around attack speed and life steal, but it wouldn't hurt to have a little armor penetration as well, which is where the armor pen quintessences come into play. When the Dominion game begins, i like to start out with a Prospector's blade (for early damage and life steal) and Boots of Speed, then I head top for the team fight. After securing top, depending on the other team's structure, I like to recall and get either Ninja Tabi or Mercury's Treads for a little defense. I then head back top for defense and fight until I either die or we kill them all. I then recall again and purchase Vampiric Scepter and, if i can afford it, an Emblem of Valour and finish the Stark's Fervor. After fighting top some more, or ganking bot to relieve the defender, I then purchase a Sanguine Blade, starting with Vampiric Sceptor. After Sanguine Blade, I purchase a Sword of the Divine for massive attack speed increase, then I begin work on my second Sanguine Blade. (Yes I understand the sanguine blade effects do not stack, however the attack damage and life steal each grants cannot be matched). If there is any time left in the game, I finish my build off by selling Prospector's Blade and purchasing a zeal, followed by Phantom Dancer. The end result of this build is 250 AD, 2.3 attack speed (2.5 when activating w), 50% life steal, and a little crit/speed boost to go along with it. I average around 15-20 kills per game and 2-4 deaths and I almost always come in first place.