It felt like everything fell into this category. It felt like if a monster had 2 abilities that called for saves, one was Con and one was Wis or Dex. I know that's not true, but it's how things felt.
I'd say undead were lots of Con and Wis (fear) saves.
Dragons were a big mix of Dex, Con, Dex, Str, and Dex saves.
I can say about halfway through Dex, Con, and Wis were all about equal (Dex actually led), so the latter half of the MM is weighted heavily in favor of Con.
Thaumaturge.
So basically, you're saying that we can use "Something from the back of the MM" as a euphemism for "You're going to be terrified every time it hits you", right?
(Or is it just my groups that start to get nervous whenever they get a whiff of negative energy, poison or the like? Noticeably more so than for any other saves)