Dies means "Is damaged by" the 50. call actually does not insignificant damage to it and combined with the Puma's low health just makes it lackluster overall.
~10% of .50 cal at point blank range will penetrate.
~4% at max range and by anything else.
And 400hp is not low, its 3 tank shots, 2 jagdtiger shots, 2 KT/jackson shots, 5 zookas, 10 ptrs shots. That is not low at all.
200 is.
Puma is anything but a luckluster, in fact puma is as effective as the player that controls it, if you are good, puma will be IMBA, if you suck, so will puma. Its most reliable AT platform below medium armor in game, which is significantly cheaper then mediums and can kill mediums, struggles only against IS-2.
You can't have a better unit in early game for AT purpose and its coax MG is pretty much as strong as single gren LMG, which is significant for AT vehicle.