I think anyone that does a lot of true damage needs to have that tuned down
The reason I think this it's because of how true damage works.
If you have problems with Armor/MR you build LDR and Void Staff, but against someone with % damage reduction like Alistar/Garen/Gragas/WW
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don't really work against them while these buffs are on.
Since true damage is so much stronger against %damage reduction, no champion in the game should have that much true damage in the kit, because it creates an imbalance.
Draven with LDR and AD/crit barely does damage to Alistar during his R, while Rageblade Vayne chuncks him every 2nd auto.
Nerf Vayne W, nerf Fiora passive, Yi E tuned down a little bit and slightly nerf Conquerer.
There are fine or even weak true damage abilities like Olaf and RekSai E, Garen ULT can be strong, but only 1/5 is the villan.

, we get up to 33. Now if we add the 20-ish total characters who can easily use conqueror and who don't already have built-in true damage, we easily get in the 50-something total number of champions who can use true damage out of 142. Even if I did make an approximation with the conqueror users (since some people would argue that some champs would use it or not) we can easily say that about a THIRD or MORE of the current champion pool possess/can use true damage. IMO, being concerned by this balance flaw is far from being overly dramatic; its logical.
As a bonus.