I don't run into them all that often, but today I ran into one that took (from me in an IL-2) 2 250 kg, 6 rockets, and more than an entire load of 23mm.  He lost... a track.
I actually went and reloaded just to kill this panzer, I started with 2 250 kg bombs, 4 Rs-132 rockets, and a full load a 20mm.  
After rearming, I used the bombs first but I dropped to low, so they didn't arm.  
I wasn't the only guy hitting this tank either.. there were a couple other guys dropping bombs and strafing.  
So is it lag or what?  This guy also seemed to have a very flexible pintle gun (about twice as flexible as the ordinary kind).  
So does my little packet say "Hey, I just dropped a 500 lb bomb on your head".. get lost in the mail or what?