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.
Before Witching Hour
After Witching Hour
DPS before 217289, Witching Hour specifies +4901 dmg
DPS after 211352, Inna's Favor specifies -3541 dmg
The actual difference is -5937 dps with the Witching hour equipped.
So it's easy to be fooled by the item compare with regards to set item bonuses