Are you addicted to making incorrect statements? Unless they change the formulas, 28 armour does NOT correspond to 28% damage reduction. 80 Armour provides 44% damage reduction. Reduce it by 28, you have 52 Armour which provides 34% damage reduction. If you have 200 Armour, it gives 67% damage reduction. Take off 28, you have 172 Armour, for 63% damage reduction.
That's not 28% more effective HP. The difference of losing 28 Armour or not at 80 natural Armour is 10% damage reduction, NOT your touted 28%.
Effective HP is not the same as percentage damage reduction.
1000 HP + 28 Armor is effectively 1280 HP against physical damage.
Look at the formulea. Right from the wiki:
http://leagueoflegends.wikia.com/wiki/Armor 25 armor → ?0.8 incoming physical damage (20% reduction,
+25% effective health).
100 armor → ?0.5 incoming physical damage (50% reduction,
+100% effective health). [If you are taking 50% reduced damage; you need to take 2000 HP worth of damage to get through 1000 HP. It takes 100% extra damage to kill you.]
Here's a video that explains it clearly too. It's an older video but the formulae has not changed.
https://www.youtube.com/watch?v=HN-d8mlsnqM#t=23s&user=DiffTheEnderDo your research before flaming. This is also why on champions who heal significantly or have shields; armor/mr are so effective. Because Armor/MR makes every shield/heal 1% better per point of resist. And why you see people usually if going for a HP/Resist item; build the HP first.
You're basically trying to say damage reduction = effective HP; which is like saying 1 ton = 1 tonne. When doing these calculations effective HP is a far easier comparative measure then attempting to work out the change in damage reduction %.
To put it simply; every point of armor makes every 100 points of HP like 101 points. 2 points makes it like 102. And so on. A 4000 HP Dr.Mundo with 100 Armor needs to take 8000 points worth of physical damage to die [50% DR]; assumeing he's not healing/hurting himself. A 200 armor/4000 HP Mundo needs to take 12,000 points of physical damage to die [66% DR]. A 300 Armor/4000 HP needs to take 16,000 damage [75% DR]. You can work out the damage reductions yourself and see for yourself.
Using this you can work out exactly how tanky each champion is from base stats against physical and magical damage. Rammus might have the highest natural armor; but someone else might have a higher effective HP against physical attacks due to a higher base HP.
For reference; Rammus has has 4,143.17 effective HP at lv 18 from his base stats against physical damage. Darius actually has 4,516.078 due to having a significantly higher base HP, despite his lower armor. [Of course in practice Rammus is usually tankier because of Defensive Ball Curl giving him a massive armor steroid.]
[Rammus = 2026 + [2026*1.04.5] Darius = 2282 + [2282*0.979]]
