How is melee and ranged damage reduction applied?

And more importantly when? So first comes armor and then all resist, then dmg reduction like aquila, but melee and ranged? is that also multiplicative with normal damage reduction?

With other words, is 50% damage reduction = 50% melee reduction?

All damage reduction, resource reduction, cool down reduction are multiplicative.
In other words, they are applied one by one. The order doesn’t matter.

General formula:
Total_DR = ( 1 - PRODUCT(1 - DRi) )