How do you guys run duels... Do you use normal combat rules or opposed roles?

Page numbers to back up your thinking please

I simply follow the rules for combat. I might embellish the narrative description, a lot, but we follow Initiative, dice pools, Destiny Point expenditure, etc. normally.

Run as normal. It can be hard with opposed rules because it can be harder to spend advantage/triumphs.

I've done them under the normal combat rules.

What helps to spice them up is not how you run the duel, but where the duel takes place. If you think about, the most memorable duels in the franchise took place in some very interesting locations, with one or both duelists making use of the environment to gain an edge in the fight (i.e. spending Advantage to either give themselves a boost die or give their foe a setback die).

The Order 66 Podcast Episode 63 is all about saber duels and variant methods of running them. Straight up lightsaber combat as written will probably be over in two rounds, or less, if the first attacker rolls well.

I found the key to a good lightsaber battles was parry and disruptive strike (I think this is the right talent- it adds failures to the enemies next attack). In essence the best fights are the ones where the sabers almost never hit, instead the victory is defined by secondary die results- such as Triumph and Despairs which force them into awkward scenarios. For example, if someone rolled both Triumph and Despair (or Triumph with a lot of Threat, or Despair with a lot of advantage) I would often rule that their lightsaber attacks the following round were ineffective and force them to take an action with some other skill in the combat (Athletics, Force Power use, Brawl). It's very important to reward creativity and to keep the fight moving- so use die results to force them out of position and to move to new locations. Allow free disengage and moves with sufficient die results (great Despair result- your opponent is considered disengaged and gains a free maneuver- don't use it to aim!).

I've struggled with this issue myself and I'm not sure how to deal with this issue myself.

I've been running Lightsaber duels as normal combat but that only lasts 1 round as the PC kills the opponent in a single strike.

Indeed, anytime that I've really seen lightsabers used in my campaign they've followed the Shadaversity "Lightsaber" trope to a T.

16 hours ago, Mark Caliber said:

I've been running Lightsaber duels as normal combat but that only lasts 1 round as the PC kills the opponent in a single strike.               

Do the opponents have ranks in Parry?

Parry & a couple of points in Adversary too. Yep.

Most memorable duel in our games was between a force user and an Inquisitor, on a gantry, high above a data storage facility being built by slave labour, whilst the hacker tried to shut down the systems, and the rest of the party tried to rescue the slaves and blow up the storage, whilst endless waves of stormtroopers arrived to recapture the facility. The duel ended up pretty cool (force user kept disarming Inquisitor then handing the lightsaber back), but it was the everything else that made it memorable.