Riot you're buffing MR items and giving more champions higher base MR, while nerfing armor items/giving AD champions easier access to GA.
I'm sorry, but the amount of games I see with all AD comps where they are not punished whatsoever make these changes seem completely nonsensical.
CannabisOverlord2 votesIf their all ad why not build armor?
Sugar Momma3 votesYou can build armor, but unfortunately turrets/baron/dragon don't build armor. And they inherently take these objectives faster than mage champions.
CannabisOverlord1 votesIm kinda on the fence on whether to agree with you or not, i ussually hit the turret alot harder on morde than i do on say, trundle/fiora/olaf, due to ap
Schàdenfreude1 votesAlso, ap champions get a spellshield now 
Very Hard Engage2 votesIf their all ad why not build armor?
people do and still lose despite doing so because of the potency of lw/cleaver combo ignoring the bulk of what you have built all game long.
SwiftKitten881 votesi do disagree with all the MR buffs... MR is already a lot easier to come by than armor.
and AP is a LOT lower than it used to be
50000000000000002 votesMR is easy to access if you're not a tank. Currently, Spirit Visage is pretty much the only good tank MR item. Armor is very easy to come by for a tank.
That said, it's definitely true that magic damage is getting indirectly nerfed pretty hard. Hopefully Mpen gets buffed and Arpen gets nerfed to adjust for this.