This is ridiculous. Fiora's hitting vitals for 800 true damage, Master Yi deals almost half true damage, Tryndamere deals over 30% true damage, Camille exists. Ignite randomly gets buffed by 50% to deal over 400 true damage mid game. A support has a true damage execute for 33-45% of your max HP. To top it off it feels like it's affecting champion design -- you gave Irelia an ability that's only countered by true damage while she's channeling it, since it's uninterruptible and gives a massive normal damage reduction.
This is stupid.