The build is standard and good, however the main issue i personally see with the guide is that, you are trying to teach people to play the character, they could be veterans, but you cannot assume that, you must appeal to a wide range of players. In reality the people that come to this website to find builds are those who are inexperienced in the type of game and , or , new to the game. As a result i see little point in publishing a build which at every turn says "obviously" as an explanation. Players who want to learn a new champion, in this case kayle shouldn't have to be dumbfounded to why you say "obvious" to thornmail for example, for, to some people it isn't obvious and you need to say why, and justify yourself. Maybe say thornmail is great against ad teams BECAUSE it works to return some of the damage champions such as master yi deal in huge quantities in addition to giving you armour to defend against that damage in the first place. That would leave little gaps in a new players mind in WHY, they need to buy and item and WHEN they need to buy an item. At the moment, i feel that your guide is seriously lacking in this department and new players shouldn't suffer because of your laziness to write out a bit extra.
However, i am upvoting your build as, the build is solid. It works, and i can vouch for it, for i have used it many times, and that is the only reason which i am upvoting your build, and i would be surprised to see others up vote it further if you don't make some serious overhauls in the explanation and text department.