got so tired of accidentally killing lydia because she'd jump right in front of me to melee, i took away all her melee weapons. now she pretty much has no choice but to stay back.
of course, then she proved me wrong and jumped in front of my shout and died.
do NPCs level? i think i'm going to have to research cause if they don't, i need to find one closer to my level.
also, if you do a prison break quest with a bunch of npcs, don't even bother trying to kill things. melee, magic, whatever, inevitable, you are going to hit someone and unlike other npcs, these ones (at least for me), will immediately turn on you (while others might ask wtf is up wit dat?).