Why Does Riot Keep Nerfing Armor Pen?

>** Lord Dominik’s Regards New Recipe: [Last Whisper + Pickaxe + 625 gold] Total cost increased from 2600 to 2800 Attack Damage lowered from 50 to 40 Armor Penetration changed from [35% bonus armor penetration] to [35% total armor penetration] Giant Slayer passive removed.

>** Mortal Reminder Gold cost increased from 2600 to 2800 Attack Damage lowered from 50 to 40 Armor Penetration changed from [35% bonus armor penetration] to [25% total armor penetration]

Its already hard enough dealing with champs in the mid lane that get items like , not even mentioning the bruisers and tanks that get 425+ health in their items. Imagine being a player like me, with 1800 health late game while Trundle sitting over there with 4.5k health able to kill me in the matter of seconds and I cant even counter build using Lord Dominiks.