Not really. In Crota it drops heavy a lot. You can prove this yourself by simply doing the first part (the crystal) with no heavy ammo. Kill everything and you'll notice that you end up with a tonne of heavy ammo drops. It's always done this! The key is not to cross kill i.e. to kill the enemy yourself and not have others shoot the same enemies. Even a titan with Ruin wings can make a virtual infinite amount of heavy ammo in crota. Seriously do you guys really think that simply having no ammo somehow makes the game create an infinite amount of heavy ammo. How would that even logically work. You can't accidentally program that i.e. if ammo empty create heavy ammo drops only...really!