If you're blazing through a map with a "superpair" your units are already powerful enough to take on the map with ease. You probably don't need the pair up system to do it. Its in difficult maps that the complications shine. The early lunatic maps come to mind. While rescue is there to primarily undo your mistakes, the pair up system adds more depth to combat. You get a more powerful pair when paired up but you also lose to ability to attack with both. Its a more defensive stance while rescue is either "oh shit, I didn't think things through" or "I'm gunna transport this guy across the map".
One of my rules for my lunatic run was that Frederick was not allowed to ever be declared the map hero. I can tell you those first 6 maps were a hell lot of fun and extremely hard. I had to thoroughly plan out my actions and the pair up system added more possibilities, although it was not always the best choice. It would not have been that engaging if it were not for the pair up system. Rescue really would not have depend the experience.