Ok, the argument that the hero does die: the two times that she has, Joss knew he was going to bring her back. She died against the Master because it was the end of the series and it was like 'oh' and then she got revived - same for The Gift.
And regarding Luke - Buffy had NO idea what she was doing in Season One especially the two part opener. That's what those episodes were about. She didn't want to be a slayer and she didn't know what to do. She knew there was no way she could have fought Luke physically and that was why she had to do what she did. Thinking on your feet because you know you will get beaten to pulp if you try to do it physically, does not in my opinion, make you a good fighter. It makes you a good thinker.
Personally, I think the whole way that Buffy works is that she initially gets beaten up, very badly the first time she comes up against an enemy (Luke, The Master, Adam, Glory, Turok-Han and Caleb) and then it takes the help from everyone else; magic etc in order for her to defeat them. If she was the BEST fighter, as opposed to a good one, she wouldn't need anyone else. But that is what the show is about; she has lived longer than most slayers because she is not alone.