The M3 was designed to stop a .50 cal at 500yds from the front, wasn't it
?
Also, the whole issue with saying "But the crew died!" is that one lucky bullet won't kill the entire crew, and that if one crew member is down, it won't opperate at full efficiency. Basicly, its all or nothing, which is the problem; not that its too hard or too easy to knock out.
Personally, I say we introduce magazines to the wirblewind and ostwind. With the wirb, all 4 will start out loaded, and you can fire all four at once. However, due to the reload, you cannot fire all four at once with continuous fire To allow for continous fire, we could have one pair be reloaded at a time, so that while the one pair is being reloaded, the other can fire. Obviously, if you stop firing, and let the loader catch up, you can fire all for at once again.
For the crew/damage thing, if a pair of guns is hit, it stops working. If the loader is hit, reloads take longer (since its whoever else would be up there in the turret filling in).
That way, we can model partial damage, and still keep the wirby functioning relatively close to how it does now.
