I am surprised the He111 and Lancaster do as badly as they do, respectively. He111 is doing worse than the G4M1? Ouch.
While the He 111 is way more sturdy than the G4M, it doesn't matters as much as one could think. The plane is so slow and so badly armed (single 7.92mm MG's with only ~500 rounds per gun, you can't even blast away) that almost any fighter can do repeated attacks until it's finally down. The 20mm in the front doesn't really help, that's not the place most attacks come from.
The G4M on the other hand has actually somewhat of a chance to fight back with its 20mm tail gun. If the Heinkel had a similar installation, the numbers would be quite different.
If I look at my personal experience... I have similar loss rates in both planes: I lost 18% of my G4M's to enemy planes and 20% of my He 111. The main difference is having a K/D of 0.17 in the Heinkel while having a K/D of 0.47 in the G4M. The Betty can at least fight back!
(Interestingly I have about the same loss rate in the B-17, but of course the K/D is much higher there.)
But in the end, these numbers are totally what I expected from the He 111, knowing it's performance data and armament.
Slow climbing & flying, underarmed and too low of an OBJ to be an effective perk farmer we won't see much of it in the LW in the future. I think it will get chosen for a ride mostly based on the looks and not any performance aspect.