If you really want to make tanks better Riot, you need to lose your obsession with true damage
Buffing tanks and items with more armor and magic resistance honestly does nothing when you hand out true damage like candy. Honestly before Conqueror came out it felt as if true damage was a rare, hard-to-work for damage type really only achieved by building full penetration items. (With the exception of champions that have built in true damage such as
etc)
But tanks started doing really bad when Conqueror came out and 20% true damage on attacks became a thing. If a tank can't itemize against it of course they are going to do bad. The new conqueror of course lowered it to 10%, but it still exists and makes tanks which should require at least two to kill, be instantly shredded down.
Tanks shouldn't have to be buffed over and over with damage - why is something meant to be a wall with cc doing damage like a truck? Leave that to mages, assassins, adc, fighters. But giving them more armor/magic resistance also doesn't help. Giving
13% true damage isn't helping the situation. Neither is giving
more damage. They are meant to ABSORB damage for their team, not deal it for them!
I feel as if the problem is true damage. It doesn't need to be everywhere. Kayle's final form has it and sometimes I wonder why, she can already scale out of control after level 11. You find yourselves nerfing her patch after patch and it does nothing to her place at the top of the top lane because - you ignore what is the real problem and nerf what isn't.
Giving champions like
who can already snowball out of control but thrives on burst damage, sustained true damage and even more healing is so unnecessary.
is another example.
If the argument is that before Conqueror that tanks were just too much to deal with for fighters can't you make the counterargument that a fighter should work in the early game to try and shutdown the tank with jungle help so that they itemize faster? Giving them a true damage rune nullifies the tank having ANY chance.
Also, just a side note. Instead of buffing champions that are performing poorly with more damage, why not just...nerf the damage of champions that do too much to bring damage down as a whole. Just a thought.
Like you gave an on-hit ranged champion true damage EVERY hit! 
I mean come on.