It must be because Russian helos suck!
I did up a quick mission using a UH-60 and it's stable and stationary at 1000m. I'll work on seeing if it can be adjusted up to 2000m. When I tried to swap forces out for OPFOR, the Mi-17 started crashing no matter what altitude I set it at...
But anyway, here you go, HALO practice from 1000m quick and dirty.
Edit: Setting the UH-60 to 2000m leaves it stable at 1500m, so maybe that's the max ceiling for AI helos?