Looking back at Luke and comparing him with what vampires quickly evolved into on the show, yeah, he does seem to have an awfully low tolerance for pain, especially for the kind of nearly mindless brute that he was depicted as being. I can't imagine him holding his hand out in the sunlight and laughing as it sizzles, the way that Angel did, or picking up a cross and hitting another vampire the way that Spike Spike did, in "Destiny," in the last season of "Angel," eight years later. It kind of makes, "You're strong. I'm stronger," seem like little more than mindless bravado.