Return of Reckoning

Hi.
Not sure if it's bug or wad but when I use (on my Chosen) for example toughness potion, that brings me up to 800 toughness and then use toughness aura that gives 102 I then in total get 852 and not 902. The same goes with resistances.
Any ideas?

Auras don't stack with potions.

If you're below lvl40 then your stats are already in soft cap threshold and thus being divided by two.
And buffs don't stack with pots (anymore).