It also seems to disregard set bonuses on items. I bought a Witching Hour belt yesterday that showed me a 4k dmg increase, but when I equipped it it gave me -10k dmg. My Inna belt still showed less dmg when I had Witching Hour equipped. Until I put it back on.
This can be a costly mistake to make and should really not be a issue. This should be fixed as soon as possible.