Not bugged. It has 7/6/5 penetration. AP rounds give +200% pen so 21/18/15 pen. That's great for killing half tracks and 222s but the Luchs has 55 armor. That's a 38%/33%/27% chance to pen for 10 damage per bullet vs Luch's 400 health. DSHK also has pretty low ROF and burst durations.
The M2HB barely does any damage to a Luchs either and its AP ability gives increased damage too.
As for Ostwind versus light vehicles, I wouldn't call this melting (15:15m):
If it has 15 pen on max range per round every 4th round should pen and do damage. As I said. I had a dshk shooting at a Luchs for like 20 seconds and it did nothing despite being on AP rounds. How is this possible. It felt like the AP rounds were not activating despite using the ability.
And for the clip: Both vehicles were moving and the Ostwind missed most of it´s long-range shots. Close the distance and stop moving and voila it will melt them.