I don't know if you played DOS2 or not, but your character was not permanently dead if teleported into lava.
Anyway, the overriding point is that anything players can do, npcs should be able to do as well (from an AI stand point).
No, but in D&D a character that falls into lava will pretty much be permanently dead since there's no way to extract you in most cases. Sure, if you have a wish spell or (or some other very powerful magic) you could save them but that's about it. The other option is that they veer further away from D&D, though I don't see that as a good solution either