[Griffon]

Dora9, are you referring to Hptm. Robert "Bazi" Weiss?
AFAIK, he was killed in a big furball with a superior number of Spitfires, but that does not say anything about bad qualities of the Dora9.

Also, LW Aces were not simply allowed to choose their fav plane, they had to fly with what their units were equipped!
probably a better example of a LW top ace who was not successful in the Dora9 is Gerd Barkhorn, who did not score a single kill while flying the D9.

Heinz Bär on the other hand may have shot down two Tiffies/Tempests during Bodenplatte, but it is not entirely sure that he used a Dora9 during the assault.