Dunno much about dueling, just owning everyone in the area until you meet a real duel build
I think you would want to max lucky hit chance and maximize crowd control effects. There are builds who outleech and outdamage any Sorc, so Firewall build is probably hit and run, so you want to spam Teleports and Firewalls (Mage's Firewall with Crippling Flames) and never lose unstoppable and catch your opponent on your Firewall at the moment when he loses unstoppable.
Maybe Oculus is quite good for this and Fists of Fate/Frostburn. I imagine you don't need too much damage aspects as it's DoT effect should be enough. So you probably want life/dr on your gear. I would also keep Tibault's and Shako for uniques and for aspects something like Searing Wards, Snowveiled, Fortune, Engulfing Flames, Smiting, Exploiter's. For vampyric Metamorphosis, Undying, etc.
Then I would mix some sort of stun or freeze into the build via enchantments which automatically casts some lightning or frost skill.