The undead change had me so hyped for playing in evil biomes, but the surprising difficulty (face-melting weather, undying zombies, vampires almost always killing their food, etc.) had me genning worlds without vampires and playing in good/neutral biomes. I really wish that headshots kept zombies dead, btw. The whole "they keep coming back" thing was beyond just weirdly non-canon, it exacerbated the whole "peasants fight literally nothing and instead run" problem.
Vampires are ubiquitous to all old civilizations, not evil biomes. Face-melting rains are very much an obstacle that can be easily overcome (and exploited!), vapours are something terrifying but not always crushing (they have been weaponized!) and the reanimating dead is not a constant, nor is it something that instantly equals Fortress destruction. There are many,
many ways people thrive in those Forts.
I'm not quite sure what got you hyped, because most of the changes increased the chances of difficulty and the ranges of interactions of evil biomes. It was quite specific.
As for the headshots thing, abandon all ideas of your "canon" things and "this is how it should be." DF creates its own fantasy, anything not done by Threetoe, Toady or DF itself is not DF canon. Anything done by them is.
I once decapitated a human corpse zombie, it still kept shambling after me... This is canon. I once butchered a yak, its skin tried to strangle me... This is canon. How do bits of bone come back to life to kill me? This is canon!
Though yes, it does not make sense how something
so broken can keep coming after you. It is puzzling.