He was good,but Salvador Dali would be better if Jodorowsky made his version.
P.S Yuech even as trusted doctor could not get to both schield generator and comm center and kill crews of both sites,after that taking Prince alive.Nor he could poison them,he was not responsible for their food.
Jodorowsky's dune would have been very popular with art critics and people interested in the purely technical aspects of the film, but the Talifan would have been pissed, and it would have led to a cult classic and a split base at best.
As to Yueh, well there is nothing to suggest he was good at combat, maybe his knowledge of physiology, close contact with the Atreides new army, and his Bene Gesserit wife combined to give him enough of an inkling into Prana-Bindu/Weirding, but there wasn't anything to suggest Suk doctors were capable fighters.
Maybe he just had to tranquilize the guards and take out the shield generators, he was adept at medicine and poisons, indicated by that poison gas tooth he used, maybe the Harkonens had more special the hidden for him to use, something akin to the hunter-killers.
Herbert didn't go into specifics.