In certain situations, the order in which Warrior CP is assigned appears to affect damage calculation in both PvP and PvE. It appears that putting points into Hardy/Elemental Defender before Ironclad/Thick Skinned is the safest method.
In the image below, I show the damage done to me by Bloodspawn's Claw attack first with no Warrior CP assigned (5349, 3387 damage). I then put 100 points into Ironclad and then 100 points into Hardy and take 3424 and 2168 damage (~36% damage reduction). I remove all my Warrior CP and then assign 100 points into Hardy and then 100 points into Ironclad and take 3210 and 2033 damage (40% damage reduction).
This phenomena is reproducible in PvP. The image below shows me taking 2235 damage from Crystal Fragments with no Warrior CP assigned. This is reduced to 1431(36% damage reduction) when 100 points is invested in Ironclad then 100 points in Elemental Defender. Swapping the order (that is 100 points in Elemental Defender then 100 points in Ironclad) results in a damage of 1341 (40% damage reduction).
Further testing on the PTS suggest that this non-commutivity appears when there is significant investment in Ironclad and Hardy, specifically when the sum of floored tooltips reaches 25, 29, 33 and 36.
Edited by Asayre on May 27, 2017 10:44AM