Non-shield offhands: The only usefulness I've found in them is to switch them in during a boss fight after I take a few hits on my HP, for that extra punch to get the boss.
@Ungin: I completely agree. After you finish the last quest mob, you should return for reward before automatically going to rest. The reward might cause a level and fully heal, which saves the rest time. It is a small thing. But it annoys me when I see the character rests when it's obvious the quest reward will level him. Getting HP fully healed and keep going on during a level up was always something I always liked in any RPG game :)
Rogue's Duel Wield: Doesn't it seem really weak for very small Agility gain? Even not considering the talent points, it's not really worth giving up the extra HP from a Shield.