Ulic Qel-Droma has been compared in swordsmanship to DE Luke and was infact a prefiguration of that Luke incarnation, Exar Kun depending on weaponry is either a perfect equal or a slight superior.
Dark Side DE Luke Skywalker has never faced an Exar Kun type of duelist nor anyone even close to that style yet, unpredictability and trickery is the name of Kun's quite unique game. Luke however is exactly the type of duelist Kun is used to engaging, a high tier Form V master and has nothing to show Kun that Kun hasn't spent his life learning to best.
In terms of speed I would put them on a similar tier, stamina goes to Exar Kun, durability is about equal and strength goes to Exar Kun.
Exar Kun's force power has demonstrated powerful Force Defenses easily able to tank bombing runs, reflect sorcery attacks and shrug off Sever Force attempts. Luke's Force defenses as of this point are roughly equal, tanking AT-AT shots and somewhat blocking Palpatine's low-end lightning bursts are both very impressive.
Offensively however, Luke has nothing to throw at Kun that Kun won't expect whereas Kun has a whole bag of sorcery that Vader, nevermind DE Luke, doesn't understand the first thing about and would be game-changing.
Lastly Exar Kun has a high-tier precognition ability that Luke can't over come nor match in efficiency, everything Luke does Exar will have prepared a counter for.
DE Luke + Leia's battle mind + Anakin Solo & Leia Organa Solo's amp barely made the difference to stop a DE Sidious who was essentially caught off-guard.
Is quoting the powers of an extremely powerful Dark Lord of the Sith whom has been placed above Darth Vader and even suggesting that he might beat DE Luke over-estimating? I hardly think so.
He said Ulic was a prefiguration of Luke as a result of numerous similar traits (ie. excelling in lightsaber combat, the rashness and impulsiveness of his character, etc.).
The comparison was of the numerous characteristic elements that were similar between the two, but the most he said regarding their skill was that they were both excellent swordsmen. That's all. That, combined with their character similarities, is what makes Ulic a "prefiguration" of Luke. That's all he needs to be an indication of a future character (Luke), which is all he says. In other words, they're comparable as characters due to the number of traits they share. "Excellent swordsman" is a pretty ambiguous and not exactly overwhelming accolade. Ulic has better, to be honest.
Also, where does he mention that it's DE Luke he is talking about? Somebody else told me he was comparing Ulic to RotJ Luke.