Flat Magic Pen and ranged MR

Ranged champions have a rough MR between 30-36 and with the removal of MR Runes, ANY AP caster can just buy Sorcerer Bootz and Liandrys, thats basically 33 FLAT MR Pen, add in a Void Staff and you'll have negative MR since unlike LDR or Mortal Reminder, Void Staff isn't BONUS Magic pen. I feel like there should be a nerf to flat MR pen or maybe have ranged champs have +1 or 2 MR/lvl