Major damage bug on warrior gear

[mitno]

When i equip Magma claymore assault instead of Maul i loose 160 damage but my skills damage go up. It is not only happens in display, I also tested it in fight and the result is that with claymore I hit distinctively harder.
I always thought skill's damage is a derivative of damage stat, isnt it?
Here are screens:
With maul:


with Claymore:


p.s. it happens not only with Claymore, it hapens with all lvl 40+ warrior weapons.