Unfortunately, you are the one twisting the numbers due to your inability to understand decreases in incoming damage. No amount of winky faces in your message can change that.
Lets pretend 2 tanks (tank A and tank B) are currently tanking a monster (monster X). Monster X has an attack that deals 100 damage per second. Tank A is a tank that has been balanced around having high mitigation, and has 98% damage reduction. Tank B is a tank that has been balanced around having low mitigation, and has 8% damage reduction.
They both tank monster X:
Tank A: 100 dps turns into 2 dtps
Tank B: 100 dps turns into 92 dtps
Lets pretend that tank A and B are perfectly balanced around these numbers, because tank B has ridiculous self healing and a huge hp pool, while tank A has neither.
They both gain 1% damage reduction (tank A 98 to 99, tank B 8 to 9)
They both tank monster X:
Tank A: 100 dps turns into 1 dtps
Tank B: 100 dps turns into 91 dtps
What happens? Tank A sees a HUGE survivability increase. The damage he is taking is cut in half, and it is very noticeable. Completely busted mitigation increase. Tank B barely feels the buff. It is a buff, but a barely noticeable drop in the bucket.
If you've ever played D3, scenarios like this were common in that game. It really made me appreciate minor mitigation upgrades like .1%, because it would actually feel significant.