NPCs can not die directly from rot; they just drop to 1 HP.
Bairdotr is immune to rot from the start, if you have her in your party.
Awesome thanks! I made my main a Ranger so no. I haven't been using the two new Companions. My plan is still to go on a pickpocket spree with at least one of them, but currently I made a very very large amount of money by un-hoarding so I'm good for a while! Have 39k after buying books!
The good thing is the next time i do the rounds I can buy up all those Sextants I always see and skimp on.