Weird weapon issue?

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For some reason it wants me to use Voldrethar in my offhand instead of my heroic Dual Blade Butcher. And thats without locking anything. Except when I manually change it to offhand the DBB instead it shows a higher percent gain, +9.65 instead of +7.06. Why would it want me to use Voldrethar offhand it seems like it would just be worse, like its stat spread is almost the same its just a lower ilvl weapon and a sword instead of an axe.

I’ll take a look… some of these cases are a bit tricky where the mh and oh can have different expertise values.