Hostile NPCs only target my friends, not me

Q: When we're in combat, the NPCs only target my friends and not me

A: That may happen if you've already killed the mobs in your own savegame.

A: Some users have had success with this mod. Use at your own descretion. Refer to this and this for the reasons why mods can be a bad idea. Current status of it's compatibility can be found here.