They are losing lots of FOs due to a few reasons:
1. They get 90%+ of their captains as external direct entry, which means time to command can be as much as 7-9 years! A lucky few have got it in 2.5-3.5 years, but they are the exception rather than the rule. Plan on 4-6 years to be realistic. Just recently they interviewed 40 of their own FOs for command assessment and apparently only deemed 4 worthy. Go figure.
2. They have a strange and incredibly unfair pay scale in place that sees turbo-prop captains with thousands of hours of multi-crew PIC getting paid significantly less than inexperienced pilots with 1500 hours right seat on a Lear Jet.
3. The package on offer is the worst in HKG.