Here is the link to the patch notes on League of Legends official web.
Some noticeable changes are:
* Ezreal – being nerf again!!
* Katarina – being tweak
* Miss Fortune – ultimate (Bullet Time) being nerf
* Olaf – remove armor pen passive to active bonus on ultimate (Ragnarok)
I assume these changes are based on the latest IEM and LCS ban/pick results. Due to how popular this champions are on ban/pick.
There are more changes to look into and also in the item’s recipe as well.