During my game I ran one of the scenarios, and boy did it fail hard. It taught me that these need to be developed a little bit stronger before you introduce them to the players.
I ran the "Whack-a-mole" situation. The Bad Guys were doing some rituals to empower a summoning. It took about four minutes of explaining because of bad communication ("Wait, we only have 5 rounds TOTAL to stop 5 different places?")
Then they started asking questions for details:
"What is it we need to do in order to stop the site from activating? How many actions or rounds does it take?"
"If we break the site from activating, then can they just run back in and re-activate it?"
"If the minions and non-minion engage us, then shouldn't the activation stop, considering they're busy fighting us?"
"Can't we just see where they're going to put things up? Okay, if so, then why can't we just split up and send one guy to each site before it activates, and then just try and keep them preoccupied?"
While I came up with answers to each, it still came off half-assed. I wasn't sure how the answers would effect how the scenario played out.
I also couldn't think of actual obstacles which made movement between the sites important. I placed difficult terrain and some general setting pieces, but the PCs just went around them.
Thank God I have a giant battlemat (4 foot by 3 foot) in order to make it doable.
In the end, it felt very pointless (but slow), because the PCs weren't too challenged; they'd just sweep in, ignore the badguys for the most part, and stomp the necessary materials, then flee. And they would also start attacking a site before it activated because they succeeded in the 'tell where it's going to activate next' roll.
The lesson I took from this is: make sure to flesh out all the details first, and think rather hard about the actual way it works in play. Anticipate some of the player's questions/thoughts, or try to fill as many questionable gaps as possible. Write out the details ahead of time in a clear sheet, instead of trying to explain (and re-explain, and in effect muddy the water when you re-explain). This should go for all of the situations.