So lately, most of the champions that have been reworked so far have had percentage damage added to their abilities, so why? I don't see how it is healthy to the gameplay to add percentage damage all over the place and expect it to be normal.

First things first, the champion that seems to rule over all percentage damage is Vayne, but then again that is Vayne she is an ad carry who is met to deal tons of damage to tons of enemies.

Then we go to nidalee and gragas. Why would you add so much percentage damage to these champions? nidalee can deal 20% of current hp with only a trap, and gragas can deal 12% of your maximum hp with just pressing w. It feels like warmogs armour is just be targeted and slowly taken out of the meta. Every match at least one champion has percentage damage (which is to be expected) But why are more champions with percentage damage being added?

Gnar recently got released and the amount of percentage damage he has is insane. I don't what the thing is about percentage damage, but seeing it everywhere in summoners rift is getting quite frustrating. I used to build lots of hp items when not many champions used to have percentage damage, but now i have to build heaps of defensive items which pack tons of armour and mr.

Now then lets talk about the problem with "percentage damage".

Im a tank, i have 3.5-4.5k hp with at least 200+ armour and 100-150 Magic resist or so, i step over a nidalee trap (who has only got 30 ability power), when i stepped over the trap, I took 200+ damage per second going to a max of about 700 damage. Im versing gragas he used his w and hits me i take about 500 or more damage. It seems like riot just wants to remove tanks from the meta by adding all this percentage damage it kinda sucks for a person who does use lots of tanks/bruisers etc.

So what could be the reason for adding all this percentage damage? the only thing i could think of is that riot just probably wanted to fill up the space of a certain ability so they just added percentage damage.

Because of all this percentage Full tank kind of champions have suddenly stopped being seen, But the other reason for that is probably because they are not to good for the game right now. But right now full tanks are kinda worthless. The champions who deal heavy percentage damage are in the meta right now, making tanks worthless, not to mention vaynes unique percentage damage cannot be countered.