There seems to be something wird going on with the Actor Value "DamageResist" on Followers:

In the console, I can getav damageresist without problem, but i cannot set it.

When changing the race of a follower, all his stats update to his new level. Save for his damagereist, which does not change.

I was trying to fix the "marked for death" bug, where your follower's armor would permanently remain at -1300 after being hit by the shout. However, unlike most other follower stat problems, this is not fixed by switching races back and forth.
It is also apparently not fixably via console.

Any thoughts?

According to the http://www.uesp.net/wiki/Skyrim:Marked_for_Death, RestoreAV can fix the problem. I just tried it and can confirm it works. I assume it can work through the scripting functions as well.

Ok, thanks.
Any idea why restore would work when set does not? I never thought about trying restore because set should work in any and all circumstances...

Well, I'm guessing that the game applies DamageAV to actors when the magic effect starts, and there's a problem when it ends so that instead of RestoreAV, it does DamageAV again (but much higher that it was initially). Since SetAV would only change the base value, it doesn't seem to have much effect.