The only way to truly trouble the prime Duran is if you don't let his feinting jab control the fight.
If you can't, you lose.
It's that simple.
See 0:54, you don't simply hit Duran.
From all the aggressive fighters Duran simply has the best defence, and when he deliberately tried not to be hit, see round 15 of the Leonard fight or other later parts where he was mocking Leonard he was very difficult to hit at all.
Also can you name one fight after which Duran had a very swollen face?
His face is prove of his great defence.