MR items need buffs, especially tank MR items. This is why tanks are so weak right now.

Mage itemization is very good right now, and MR items are lacking, especially with void staff giving 40% magic pen. The highest armour in 1 item is 100, while the highest mr on 1 item is only 60, and that item is a mage item. The highest for tanks is a measly 55, and that number gets chopped to 33 since every mage build incorporates void staff. 2 of these items also have really bad hp values. With this in mind, unless you are ornn, you can't get more than 100 effective mr without heavily sacrificing physical durability. Here are my suggestions for mr item buffs and ap item nerfs: MR item buffs: Spectres cowl mr increased 25 -> 35 Spirit visage mr increased 55 -> 65 Adaptive helm hp increased 350 -> 425, mr increased 55 -> 60 Abyssal mask hp increased 350 -> 425, mr increased 55 -> 60 AP item nerfs: Banshees veil now builds from negatron cloak, ap reduced 75 -> 65 Zhonya hourglass ap reduced 75 -> 65 Void staff magic penetration reduced 40% -> 35% Sorcerer shoes magic penetration reduced 18 -> 15 Rylais crystal scepter ap reduced 90 -> 60, hp increased 300 -> 450 Rabadons deathcap cost increased 3600 -> 3800 Archangels ap reduced 50 -> 40, mana increased 650 -> 750

There is a reason why magic damage is considered more valuable than physical damage, it's because mr items are total shit. This is why ezreal adc is going with a hybrid damage based build with ludens / gunblade. This is why you will never see an ad assassin mid in competitive.