In my opinion, the main role of the duelist is to create early engagements, as favorable as possible. Not necessarily get early kills. Some games you win all the duels, some games you get farmed. What's important is, regardless of the outcome of the duel and especially if you lose, that you create a trade opportunity for your team allowing them to grab space on the map. More space = more control = higher win probability.

The only time you should be upset with a duelist not fragging is if they're actively throwing or blatantly baiting their teammates.