The third season for League of Legends will be starting soon (it was supposed to start yesterday but I gather it's not quite ready so they've pushed it back) and they're changing a bunch of things again. They've been slowly announcing things each day and the stuff from today was particularly interesting. They want to itemize more for physical casters and their solution is to change the way armor penetration works.
As it works today they made armour penetration stack in a bad way. You can get either a flat amount of armour penetration or a percentage amount. Currently the flat amount applies first and then the percentage amount. This means the percentage reduction is working off of a smaller amount and therefore is a smaller reduction. They're changing it to apply the other way which means more armour will be penetrated now than before with the same item build. This means that flat penetration items won't just be an early game thing now and will actually be really solid late game. Especially against a team with a ton of armour.
On top of that they're adding in some items to take advantage of this change. A lot of details haven't come out yet, but they did post one remade item. Black cleaver used to stack up 15 armour reduction on a target each time you auto-attacked them with a max of 3 stacks. Now it's going to have a flat 10 armour reduction with a stacking debuff of 5% armor reduction stacking up to 5 times. It will also apply on any source of physical damage instead of just auto-attacks. This is pretty sweet because it will have both a percentage reduction and a flat reduction in one item. Some characters have abilities which synergize well with the change. Garen was the example they gave... He spins to deal physical damage to everyone around him every half second. So over 3 seconds he deals physical damage 6 times to everyone around him. Knocking 25% off of everyone's armour from doing this seems pretty sweet. And I like how this item should be a lot better for Garen than for someone like Yorick. Their goal is to put more item paths into the game and building specialized items like this is a great start. I'm looking forward to seeing the rest of their item changes whenever season 3 actually launches.