Admittedly I've not played very much as of the latest patch, but from what I've seen not a lot has changed. Mastery changes are nice..
Offensive tree didn't seem to change much. Defense and utility are a long stronger. That said. Being that the game is meant to be a full game at 30 everyone has guaranteed access to masteries, so for the most part it doesn't change much. The strongest will be used, and probably nerfed. A few champions will make better use of the masteries than others, and that may cause minor balance changes, but nothing substantial.
In so far as items Teemo seems to have a complete set of niche items that a great for he, and he alone. Not that malady isn't good on a few other champions, just that there are so many item combinations that suit him.
Cleaver hatred seems to be widespread. It would suit the item well to go back to being closer to it's original state. The flat 55 armor pen it had ages ago applying on debuff, and then maybe a stacking armor pen buff that lasts several seconds. It has too much instant gratification.
Ohm wrecker is a niche item.. Basically cleaver stacking pantheon's best friend.
Other items are a bit silly.