This build is specifically for play against heavy tank teams. Some people will play with Jax, Malphite, Singed, etc. and have three of those high-armor tanks on one team. This build is specifically for taking down their advantage and letting your team have a chance of killing them. Ashe is a support type role in this case, although you will get your share of kills due to massive attack speed.

Pretty standard Ashe stuff. Lots of armor pen in runes, and the 21-0-9 gives her a bit more mana to work with early game and a slight amount of gold. I'm a fan of the new lifesteal mastery, it gives her more durability in laning early, especially at mid. All her runes are designed to mid, with magic resist to help against ap mid players.

You might be upset early game because of her lack of damage. The goal with this build is to get fed really quickly from minion kills. Her gold passive helps with this a lot. At mid you should have no problem cleaning up minion kills, unless you're playing a good Cait or something. Which is annoying. By getting Berserker's and Malady first, you gain a massive attack speed advantage early, which ensures you better farming in your lane. With this farm advantage you should be able to get Bloodthirster and some damage pretty quickly. After that, you're focused on Bloodrazor. With this item, you will have no problem taking down tanks with mass health like Singed or Mord. The nice thing about this build is you have a pretty significant armor pen already, and Malady and Bloodrazor take down both of the other defensive stats. After that, it's just straight damage with IE, and more attack speed and slight, slight durability with Ionic Spark to replace Doran's blade. At this point you can kill anyone with little effort and it's game over.

While Ashe's ult and Volley are often the most used, don't overlook Frost Shot. Take it at level 5 and leave it, since the slow is just fine until later. Always activate frost shot before you ult, ensuring your target can't escape after the stun wears off. At mid, ap players will run from this combo almost every time, allowing you either a kill or free farming. Frost shot also helps you escape ganks. If you can hit a ganker with one auto attack with frost shot on, you will remove their advantage of surprise and usually be able to escape. Always turn on frost shot before any team fight. There's no downside to having it on as is uses very little mana, and your team can always benefit from the slows it gives. Basically this Ashe build is all about debuffing the other team. Between her CC effects and the item set, you can basically remove any advantage the other team has built and allow your own team to smash on them in team fights. Always hit the tanks first with a couple of Frost Shots, which will apply the Malady debuff. However, don't focus them. Hitting them a couple times will often scare them off your carries. Then of course, you need to focus the other teams carries and you shouldn't have a problem with them. This build is also perfect for chasing down enemies, as well as preventing them from chasing down your weakened teammates.