That's assuming Luke will expend any energy defeating the others. Which, by DN? He more than likely will expnd very little. And for a Jedi meditation, you can need anywhere from knutes to hours to repair yourself, someone like Luke could recover fully, especially as none of these are hard fought victories
I'm not a fan of Luke Skywalker, but I think he'll make it all the way. Consider how he gains power, from experience, and where does he gain experience? From destroying people, I hate to say this, but beating Ludo Kressh and DE Palpatine would not only challenge Luke, but it the 10 hours that he would spend reflecting on the whole thing might give him the mental boast that he needs to defeat Ragnos. He'll make it all the way.