Of course, it was disaster all the way with low number of real kills and high number of destroyed and damaged Defiants by enemy fire.
Well, considering my initial post, all you are doing is just repeating rubbish published by others about a subject you know little about. The official claims for the period of the Battle of Britain was 19 E/A claimed for the loss of 11 Defiants. As a day fighter, the total balance was 86 (or 88) E/A claimed for 32 lost to all causes, including accidents. These are, of course official records from the time and don't take into consideration research carried out since the war.
The question as to why the Defiant was kept as a day fighter for as long as it was is easy to answer; the British had their backs to the wall - FC needed fighters and on paper including two Defiant squadrons, even Gladiator squadrons was better than not having them at all. Bearing in mind the type's weaknesses, perhaps it would have been prudent for the type to have been based in Scotland, where single seat fighters did not have the range to counter it. But, as it is so easy to look back with hindsight and question the decisions made at the time, all we can do is speculate.
There is a good little monograph about the Daffy as a day fighter by Allied Wings; No.8, by Phil Listerman and Andrew Thomas and they've taken the leg work out of the statistical side of researching the Defiant's record, and the authors quote the files accessed for the information presented. Also, check out Air Britain's The Defiant File by Alec Brew, who is the Boulton Paul Heritage Society's researcher who has listed the fate of every Defiant built from the RAF's Aircraft Movement and Accident Cards, which are kept at Hendon, as well as operational records.