https://www.vlr.gg/222239/duelist-is-the-hardest-role
The hardest role isn't duelist at all.
Reality is the hardest role in a team play game will probably always be your initiator or flash player, they always have to be ready to use abilities in the best way possible for your duelist to rack up clean kills off util.
I'd say it goes Initiator > Flash > Sentinel > Smokes > Duelist
Doesn't mean anyone playing said roles sucks or that its easy to pick up duelist it truly isn't you have to always be the best player in the match (the 'star' player) but in terms of team play initiator or flashes cleary is the hardest.