Not Updated For Current Season
The masteries shown here are not yet updated for the current season, the guide author needs to set up the new masteries. As such, they will be different than the masteries you see in-game.
This is a very basic survivability/DPS build for kennen. With this build you can take some damage due to the health, magic resist runes, and defensive masteries. While being somewhat able to survive you will still put out pretty intense DPS with your almost 800 ability power.
With this build you cant just run into a group of enemies and expect to come out alive. I would suggest wait for the tank to engage then run in with Rush, Pop your ult, and watch everyone die. Since you have Will of the Ancients, you will get some life back while your casting, so if you get roughed up a little its normally fine due to spell vamp.