The Mosquito was known to be a tough aircraft in reality.
In AH I find it to be quite tough against AA fire, but it is so large that fighters are able to hit it with a lot of rounds easily.
That said, it cannot take a 30mm round and live in AH, which it did at times demonstrate the ability to do in WWII. Of course who knows how many Mossie's were lost to a single 30mm hit.