BF fixed on live servers...

[Ooklak]

The reasoning I use to decide which to use offhand / mainhand is this:

Mainhand you want lower delay to get your damage bonus applied more, and offhand you want the best ration you can find even if it's higher just to up the damage.

This sometimes does correspond with the myth, it's not because of the myth itself, it's just what I've been told.