Oooh, I like both those observations. I am a bit surprised about the second one -- I feel like the two shouldn't correlate, although they obviously do. On the other hand, morally ambiguous immortals are my FAVOURITE. Notice also that a lot of my morally ambiguous characters are also world-saving. Morally ambiguous world-saving immortals who are also sometimes capital-g Good sort of make me weak in the knees, which is of course why I love the Doctor so much. :D

Re: magical immortals, I was slightly tempted to tick 'magical' next to the Doctor, but that's sort of stretching it, and yes, I think as character traits they'd tend to become overpowerful very, very quickly.