I know many pilots who are quite profoundly deaf - one in particular who has difficulty hearing even in normal conversation one-to-one in a quiet room.
I hear from medics of my acquiantance that it would be 'difficult' to fail anyone's JAR Class 1 on hearing grounds, and my experience with deaf pilots seems to bear this out.
As to having the option to use a decent headset, some companies prohibit use of intercom in their Ops Manuals - thus removing this option.