Vi can be an off-tank, and how I use her, a well-toned assassin. As I have played games with her, I have noticed the difference in how people play AND build her. Some people try to go to straight attack speed, and then attack damage. That would not work if you were to face another Vi using health, damage, and attack speed. That's why I believe this build is extremely useful on most battlegrounds. With this, Vi can jump into a battle, wreak some damage, and, if needed, hop out with enough health to escape.

I've heard a rumor that Riven can counter Vi pretty well. I am going to dismiss this as a rumor and that's it. If you play Vi correctly, no one can stop you.

How I play Vi: before heading towards a battle, you are going to want to charge Vault Breaker (this means to hold down) and release when the range is adequate. That's how you begin a battle, once you have rammed into the opponent, pop Excessive Force to lower even more. If you can finish the enemy off with your basic and/or Denting Blows, that's great. If not, then ult it up!

I found this build to be extremely useful in almost every match I've played. My Vi recent games are 7-0, 7-3, 9-3, 6-5, 11-8.

I discussed the abilities a bit in the notes but you will be using your Q and E most frequent for the sole purpose of jumping onto enemies. The reason I have only one point put into your W is that, it has great help, and even if it's at its first level, it's going to reduce your opponents armor every 3 hits. The problem with it though is, it is helpful for minions but you generally won't be standing there attacking a champ with your basic for long periods of time. You will be using your other abilities. Sure, the ability does stack from your other abilities, but after popping your Q and E, then getting a basic hit in, your opponents armor is reduced and a bit more damage has been dealt.

Well that's all I got, I hope this discussion helps, happy face-punching
~banditl0rd