About pilot rescue missions, I think the difficulty would be extremely different depending on terrain (farm = good, flat iceland = bad) and random map generation (placement of cover and enemies)
Randomness has a chance of creating extremely interesting situations, but there's no minimum guarantee : Like the "small scout" mission, a lot of times, you see the alien first, you shoot, it's over.
Personally I would be totally OK if a rescue mission is successful in 2 turns without even seeing any aliens. I know that the next time it could be hell, losing half the squad from a grenade.
For variation, you can have the pilot initially stunned (aliens totally ignore stunned humans), so you have to heal or carry him back.