Originally Posted by Ego

On the spreadsheet, expertise is calculated individually for the main hand and off hand weapons. In game, there is only one 'expertise' stat.

I'm fairly certain that an orc using an axe in the offhand and another weapon type in the main hand will grant the racial bonus for both hands. On the same note a human with a mace in one hand and a sword in the other should be granted the 5 expertise from each, on both hands. The spreadsheet currently does not support this.

I had a human warrior friend check his expertise stat while using a sword/mace for verification, and it does indeed show that he has 10 expertise.