We (as in a group comprising CHC, Bond and BHL) did suggest to EC that there should be an aural warning anytime autopilot functionality was lost to the point the pilot had to take manual control, but so far that hasn't been implemented.
I agree. The S-92 has an aural "DECOUPLE" alert whenever any axis is decoupled, whether in isolation or in a group and whether intentional or not. That said, it was largely drven by the SAR AFCS certification, not the regular O&G market.
I was just exploring the possibility of there being a significant distraction (Master Caution) at an inopportune moment, but possibly not.
The 92 has the same problem
Not since AMS 3.2 came out in 2006, though you wouldn't know it the way most operators fly it!