I have for about half a year send bug reports about the “not-working” Mortar traits of the Engineer. I am getting tired that this has not yet been fixed, so now I will post it here on the forums instead(as doing it ingame seems to have no effect at all)
The issue is this:
Taking both the Trait “Elite supplies”(the text say that it increases range, but that is not true. It decreases the CD on the Mortar by 20%) and “Rifled Turret Barrels”(increasing damage and Range of all Turrets, including the Mortar) is not stacking.
If you take only one of them, they give their bonus as intended(so you can have either 20% reduced CD on Mortar skills or 15% increased damage and range), but if you take both of them, you lose the benefit of “Elite Supplies”.
Summary:
Taking both “Elite Supplies” and “Rifled Turret Barrels” will only give you the effect of “Rifled Turret Barrels”. The “Elite Supplies” bonus is not applied.