Just for the hell of it, I tried setting Jarl Balgruuf the Greater not essential, i.e. can be killed, but it doesn't seem to work? I type "help balgruuf 0" to find his baseID, then "setessential enter-base-ID-here 0" and then while in the console I click on him and type "isessential" but it still throws back that he is essential.

Is it supposed to be like that? That you really can't set super essential people non-essential?