Hi,
Maybe I am missing something, but I am struggling to see the use of the 1st level ability of Feint. You use up your bonus action to allow an opponent to attack you with advantage, if they do you may use your reaction to attack them after you have been attacked. But as a Duellist you want to be duel wielding, so your bonus action would mainly be used for your offhand attack.
You would be allowed to attack using your main hand instead of your offhand, but in turn you are more or less guaranteed to be hit by an attack. Or am I missing something?
Perhaps it would make more sense that your counterattack is made with a disadvantage, but if it hits you cancel the opponent’s attack?