Against a mostly AP team even if you build 3 to 4 MR items they can still cut through you like a hot knife into butter. You will have wasted all of your gold and they can just endlessly poke you with ranged magic until you die. The MR to AP ratio is really ineffective against champions like Zoe, Brand, Veigar, and Lux at high levels.
Are you joking? MR is OP compared to armor. [sg-lux-2]
think you confused AP with AD and armor m8 LUL
AP champs are just broken period, fuck trying to be any melee champ when getting hit with a barrage of slows, fireballs, lazers, tentacles, and rays of light.
All zoe and lux mains complaining as usual, your champs are disgusting by default and no amount of MR in the world can stop them, even on a tank champ.
or maybe nerf the passive on 
because its always strong unless your name is vel koz..
All AP champions become invalidated by 
early game.
After magic penetration, they become invalidated by 
.
Can you post a clip of you being bursted through 3 to 4 MR items by any of those champions you mentioned?
If you're frustrated by AP poke as a tank, try 
+ 
on for size.
Please give us more than ONE option against AD and more than ONE option against AP.
