5 to 10% of total time is a reasonable ratio to expect for IF time.
I know of boys flying coastwatch who used to log 1 hour IF on every flight for the passes they did on targets on a sky blue day because "they were on instruments." These individuals went on to fail B737 line training and the like because at the end of the day they did not stack up.
The line training and routine job of RFDS/ Air Ambulance is probably on ef the most demanding flying jobs in the world. Particularly with the shift work, single pilot, and dozens of unfamiliar destinations you may be called to at short notice; flare paths etc
One would hope that these organisations maintain their stirling safety records via a rigid C and T system that will weed out the BIC pilots.