Thinking it doesn't need to be adjusted in anyway is just being stubborn about something that doesn't make sense, both in applying real world logic and in trying to apply it to the nature of the game's mechanics.
And not considering that maybe there ultimately isn't a problem, that maybe it actually works just fine is being just as stubborn and bull-headed. Evileeyore (who I've gladly added to my Ignore list since he's about as useful a poster as notorious forum troll ErikB/Sylpheed) is precisely that kind of stubborn, as apparently the way he runs his games is the ONLY way and everyone that does it differently is WRONG, up to and including the FFG designers who wrote the game for committing the cardinal sin of running/playing the game according to the rules that they designed.
To quote George Carlin, "I believe the truth is somewhere between ' LIVE FREE OR DIE! ' and 'Famous Potatos.' Personally, I'm leaning more towards 'Famous Potatos,' but that's just me."
Like many of the truths we cling to, the status of Duelist's Training is going to depend on one's point of view. For some, the presence of the setback die in certain circumstances is apparently a transgression on par with the acts of the Manson Family, while for others it's a neat aspect of the talent that can be used to encourage a narrative element to what might otherwise be a boring "stand still and attack each round" fight, which was sadly quite common with 3rd edition D&D classes that wanted/needed to make multiple attacks on a given round; common Fighter tactic was "charge the nearest bad guy, hope to survive their attack, and then do a full-attck on my next turn" while Monks could either move about the battlefield or make their Flurry of Blows to score extra attacks, but not both.
I think at this point it's safe to say that neither side is going to convince the other. Me, I'm off to actually generate some hard data via some combat test scenarios using a pair of Makashi Duelists, both with and without this talent and see where the dice fall. I'm not expecting the setback die to be a major hindrance, since they've both got 2 proficiency dice in Lightsaber with the key difference being one has a Presence of 3 while the other has a Presence of 4, so I'm expecing the setback die won't be a thing for the Presence 4 character in most instances.