The UBT machine gun on the back of the Il-2 was possibly the most effective rear defense an attack aircraft carried during the war so hang around on the tail of one wasn't the safest thing to do.
I'm not sure what Hartman shot down most, but citing him hardly proves a point. Hartman could have shot down just about anything (he was just that good). The average German pilot would have found the Il-2 a tough kill.
And it's not like the Russians were idiots. Their fighters flew cover for their attack planes just like everyone else did.
The Yak-3s were good but nothing to soil yourself about, well anymore than any other enemy fighter. The Il-2s had a very high loss rate, to AAA and enemy fighters.
They were concrete sitting ducks...but a very good tank buster.
i'd imagine they had allot of surplus IL-2's after the war, even if allot had been shot down, there were so many there would always be allot left over................