It's a good thing you're not the third person to bring this up in the past half hour. Oh wait.
Was there any specific reason (a blue post, pvp concern or such) that they reversed the way in which 'Hack N' Slash' (Main Gauche) works? Because honestly, it seems like the easiest way to fix the whole situation is to have offhand hits proc mainhand hits again. It's not like Arms warriors have a way better system in place already or anything.
Sure it edges us back into the 'fast offhand' corner again, but it's not like there aren't two other mechanics already pushing that. If Sinister Strike hit with both weapons as every other class's melee specs main/second attack does I'd be perhaps more inclined to care about a slow offhand, but as it is? Nah.
Here's hoping combat gets another pass, but my first question still stands. Did they ever state the reason?