If we read the novel properly JY say that Yang Guo would win the fight within 200 stances (pre Jinlun cheat) at that time he even didn't use Sad Palm so even if we erase Sad Palm part I also don't think any Greats/Guo Jing would be able to defeat End-ROCH Jinlun within 200 stances..
Yes, but although YG Melancholy Palms seems to be the most powerful MA innovation in the trilogy, I prefer Tai Chi is the best since it gives more impact and can be useful for any range of martial artist starts from Wudang students, 7 Wudang heroes, ZWJ and even can be learned by the any spectators who saw ZWJ learned fresh from the author.
Melancholy Palms is only used by YG and works best only if he is sad and desperate.