In my playthrough
Isobel
went down so fast I thought it was a scripted scene that was supposed to happen like that. Apparently they did change that in a hotfix to be less likely to happen.

But I'm almost more annoyed by the fact that as a consequence,

Dammon died before I even knew he was the only NPC that would craft all the Infernal Alloy lying around everywhere. The game suggested Isobel is a priority so that's what I did first in the Last Light, and then all the other NPC's died before I could even talk to them.

And it is annoying that Revivify doesn't work on an NPC that just died. Especially when they have the habit of running straight into Cloud of Daggers after combat.