Suggested buffs to pure tanks (NOT hybrid JUGGERNAUTS) to counter the current adc meta

The current meta and item buffs for adcs to counter tanks mid to late game are very effective and sometimes gamechanging, exceptionally ad champs that deal % hp damage. My suggestion is that when a tank's defensive ability (ex. rammus w, leona w, and even malphite w) is active, gives them a **temporary **buff that halves % hp damage/true damage, all armor/magic pen, and apply a weak version of grievous wounds (20-30% heal reduction) to the assaulting target until the end of the ability's duration. This buffs should be on real tanks only, not darius, mord, garen(he already has damage reduce on his w). To make sure proper buffs to the right champs and overall game balance, this should appear on champs like rammus after they have gotten 250 total armor or 180 total mr and other champs (full tank garen?) after 150 bonus armor or 140 bonus mr.

Feel free to comment your hearts out about this or come up with some version of buffs to save the tanks from being taken out solo by an adc in under 8 seconds late game while not even breaking their bt shield.