My personal settings for air doctrine have changed over time, from 10, 50, 50, ... to all 100's. Hadn't realized what those settings meant at first (my inattention!)
Understand that #'s mean % of "normal." "Normal" means what developers considered appropriate and is not known to me (anyone?) Have used this approach in 41, 42, 43, & 44 campaigns. Personally satisfied with 100's.
In '41 (& maybe '42) Axis air victories are against very poor equipment, but by '43, SU equipment is much better. Its the pilots that matter, not so much the equipment.
For ease of play in '41, '42 I allow SU air to be defeated by self-defense rather than direct attack.
Escorted air missions against SU strong points are very useful when needed, but not so useful in general. Destroying ports at Leningrad at least is essential.
Above observations pertain to AI experience only. H2H may be different.