My brother has them - he basically runs Gjallarhorn as a primary.
When Ruin Wings work, they work gangbusters. I have a few screenshots with dozens of heavy ammo blocks littering the area.
Then they just stop. Not slow down. Stop. Cold. As in zero heavy ammo, worse than the normal drip of heavy ammo you get without Ruin Wings.
I ran CE last night, and the first part with thralls we were just killing time waiting for someone to join, and there must have been 30 heavy ammo blocks on my screen. We get to the Crota room and got nothing for 3 wipes. Equipped the No Backup Plans, equipped Ruin Wings, exited out, ran 2 more wipes and got no heavy ammo. Equipped NBP, exited out, went immediately back in, equipped RW, and immediately started getting heavy ammo.
It's definitely bugged. It's just hard to quantify if it's ALL Ruin Wings, ones acquired through engrams, ones sold on different weeks, what causes the perk to stop working, what makes it work again, etc.