Armor is useless just build health to tank

The only "tank" build left is this:

Drain tank still works at least lol

Armor may be useless, but health without armor is also useless.

If you stack armor, you'll still be instagibbed because armor just doesn't do much. If you stack health, you'll still be instagibbed because that's how high damage is.

Dont forget every 3rd hit from Vayne's W (Hint, Rageblade nerf made it harder to instagimp people, but its far from a bad item on her)

counters

Resistance hard counters those items. Their effects do magic or physical damage based on your health so you are just screwing yourself by only building health. Some math as an example:

You have 2k hp and 100 armor base.

Build warmog's for 2.8k hp and 100 armor

The first 8% current hp hit of bork will do 2800 x .08 x (1 - 100 / 200) = 112 damage which is 4% of your max hp.

Build Frozen heart for 2k hp and 200 armor

The first 8% current hp hit of bork will do 2000 x .08 x (1 - 200 / 300) = 53 damage which is 2.6% of your max hp

It's crazy how many people complain about armor being worthless when it is absolutely correct to build in many circumstances.

It should not/does not make you invulnerable, and it's not ideal on every champion all the time, but it definitely has its place in the game. Stacking health in lieu of armor is great in some situations and worthless in others.

Armor is useless but you still need to build armor items that come with defensive passives like crit damage reduction + aa slow.