WSX is actually a class act. Even after a long run of mediocre (by her standards) results, she is still ranked #5 in the BWF rankings. She has not had much top-tier match practise since before the OG, and is just getting into her groove. Can't write her off, particularly in the early rounds. Her h-h against Eriko is 4-0; the last time was at the All England 2012 where WSX took it in 2 easy games. I think she will move pretty easily into the finals, where Saina will likely stop her, because Saina appears to have figured her out. Unless WSX has learnt a few new tricks... Or unless she meets Tine Baun in the semis...
A good player should be able to play relatively well in two back-to-back tournaments but it would be hard to do so in three successive tournaments. LD, LCW CL, WYH, SN prove this time and time again. DPY did not compete in the Dutch Open and he should not be over-fatigue as he had three days to recover from the Denmark final.
As madbad had mentioned many times, it is Du PY's style of play. You should understand since you watched the LCW match. Unless you're superhuman you would definitely be burned out from that. Du PY I believe is a very fit player but with his style of play, I was shocked that he wasn't just sprawling on the floor halfway through the 3rd game against LCW.