There seems to be a misconception that the Allied fighters in the CBI were ineffective until the Spitfire arrived in 1943/44 and this is not quite true.
The Allies had (in addition to the Hurricane IIA/C and P-40B/C/E) the P-43A-1and Mohawk (replaced by Spit VIII in Jan 44, by the way) all of which contributed in reducing the numbers of IJA and IJN aircraft and pilots until newer Allied types became available.
The Japanese were feeling the pressure so much by 1943, that the 2nd Hiko Chutai pressed several captured P-40Es into service during the defense of Rangoon. This is a pretty good indicator of how things were going by the time the Spitfires were starting to arrive in theater.