The only time I have seen Opto's fail is if to much current is drawn from them or to much voltage is pushed into them. We use FOD3182's at work to drive 3phase 3HP motors and when the IGBT's go they take everything between them and the FOD3182's out due to the 700V bus voltage.

This is more a generalized design then a specific one case setup, I want to give the end user some leeway in what they put on the board. I am considering removing the dip8 Gate driver opto's since I see very few cases in which you would need to switch at the very high speeds they can produce. The on/off losses with the slower 4Dip opto's is fairly small compared to the overall switching losses themselves.

I agree that the TL431 can be a simpler way in doing it (you could just drive the N Mosfet directly to) but I have preferences towards Opto's due to the protection they provide.

edit..
Added 10K pulldown on the fet gate to actually allow it to switch on and off....
HeadBed PCB4.jpg