If anything, with future Pilots being more 'systems operators' than stick monkeys, it is only right that Observer aptitude is more important. This is why the RN insist on having passed both WELL!.
Typhoon/JSF Pilots don't need the awesome hand-eye co-ordination that Harrier pilots did - the a/c will fly itself. Instead, they will need to operate millions of systems at once which really maxes you out. I presume this is how pilot and obs aptitudes differ. Pilot being purely the hand-eye/reaction stuff, with Obs being all the horrible-all-at-once-things that make you sweat like MJ/calculations stuff.
To be blunt, if you can't do it in front of a PC in a small room, how can you expect to do it a 500 kts whilst trying to bomb someone with missiles coming at you?