For me main problem was Shkval movement in Ka-50. I couldn't use mouse and was too lazy to manually set it up in config files. In Su-25T you can use mouse so you have fine control over image movement, thus easier locking :)
Ka-50's laser also doesn't give correct distance to the locked target. If it approaches quite fast (even A-10 is fast for Ka-50... :P) then gun firing can fail due to laser's lock distance wrong numbers, ie. it shows good and suddenly goes higher or slower than before - you have to relock again and again..... your laser is being used, used, and after while can be fried :D