Ask a silly question, you get every answer.

I normally do not get into "what can I do so I can be OP" type of threads, but this one is kind of funny, as everyone has their own opinion on the matter. There is a reason for that. If you have to ask, you probably will not do as well as those giving you the answer. I mean this in that dueling is something of an art, and if you know your set weakness and strengths better than your opponent, then you can use pretty much any.
Just to toss in there, yes, a NB can use the element of surprise in a duel, though I guess your opponent wont technically be surprised..lol.
Sadly armor sets and how many/what kind of pots you have matters more than most other things. Just a fact.

I play pet sorc and duel a lot. It is very strong. So strong, many people will whine about it being so OP in duels they will refuse to fight. I consistently beat every spec within the first 10 seconds except for players who are extremely skilled. I run BSW+Necro. The sustain is crap, so if my opponenet can survive my first 3 burst attemps then I need to switch to defense for a while to regain mag. If I'm facing a magicka player this is much earier as they will refill my magicka while I spam Harness Magicka. Players with very high damage that can burst my pets down before I can reshield/heal them are usually my toughest opponents. Most of the time, though, people die before I even get to the end of my burst combo.