I have been playing a new household with a fairy and a witch for one sim-week. Both have the apothecary skill, and the fairy can cure ailments. During this ONE in-game week, the witch hadn't had negative moodlets, (though she did have bad luck a few days), yet still swung to imbalanced and ended up with ailments six different times. Twice, she got a different ailment RIGHT after having been cured of one (one time via fairy cure, one time via apothecary cure).
The fairy ended up with the gnome ailment on the first friday of the new save, so i had the witch make a cure, and looked away for a moment while she was walking across the house to deliver it to him... only to look back and find my game paused on the death screen, with no idea what had happened. There was no notification to indicate how he died (the last two notifs were about him getting repair parts from playing with the stereo, and info about his cheerful trait), though my witch did suddenly have the burning passion ailment along with the widower and grieving debuffs.
I don't think I can keep playing if the ailments are gonna be this instantly destructive and constant. They really need to turn that wildness down.
EDIT: This may be a symptom of having too many packs (because EVERYTHING and its mother gives a buff of some sort), since my sims are consistently at high emotional states (though positive ones). Historically speaking, the sims team does seem to think that we should not play with all the packs at once, and cross-pack compatibility does tend to be lacking.
EDIT2: he died of laughter. that death type ruins most of my legacy attempts, to the extent that i'm about to just start making everyone cringe.