If you are going for the Super Hero achievement, I highly advise not even bothering with this one until after you complete the game.
Why? Because, with the exception of 1 or 2 of the missions you will be handed, these will annoy the crap out of you on Super Hero difficulty.
Your best bet is to do these on Easy, and knock out 10 of them post-game. Once the main storyline is complete (and after the Super Hero achievement pops) take the difficulty down a notch or two
. I found, even with the missions that had more than 4 people to rescue, I had plenty of time to get this done with the difficulty set to easy.
Honestly, I had no issues with the main campaign, or any of the optional missions, on Super Hero EXCEPT for these events. After failing a few of them I gave up until post-game, and then got them down in ~20 minutes
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Questions, corrections and neg vote justifications in the comments below.