ehhh. i dont really feel that way. when I play Rhaast. I get a SV and thats about enough MR to keep me from melting. sure the syndra will drop 3/4 my hp with her ult, but that is because she is blowing her Ult on me.
Also just gonna say this. around 200 of a resist it stops being useful to get it. 200 of a resist is roughly 70% damage reduction. Then ofc magic pen comes in with its flat and % values. so if they are rolling a
and you have 200 MR you will effectively have 200x.6 = 120 - 33 = 87.
so as you can see its not that Magic Damage is too high. its that Void Staff is too impactful. Armor is easier to build and the % pen item for it is only 35% to Void Staff's 40% (iirc it used to be 35 i dont know why they changed it) So while MR is yes much harder to build with only 3 items being truely relevant
(which honestly I think are fine, because on top of being 55MR each, they all have amazing passives)
Also btw didnt realize this. Void Staff and Guinsoos dont work together for Pen. they both have the same Unique Passive and so the MPen bit of Guinsoos will actually be turned off if you have Void staff because league takes the higher value.