One .50cal is a fearsome enough weapon. I firmly believe that 8 of them firing on a target at once, with up to 16 or even 32 of them (two-four aircraft) could very well sling enough lead to land a round, even a few richochets, and disable a tiger.
Yes, on paper the armor is too thick and the .50 doesn't offer enough penetration, however there are a LOT of things in a combat environment that happen that nobody looking at the papers would ever have believed.
For instance, the use of IEDs in Iraq and then Afghanistan just kinda happened. Nobody saw that coming. It took a few years to develop ways to counter them, too.
I completely see tigers being disabled from strafing runs as a very plausible outcome. Not as good as a few bombs, but good enough. One less tank for the guys on the ground to deal with, the better. Even if it's not fully dead, and even if the crew gets away.
My two cents.