I want logical behavior.
A dragon circling me for miles and then just flying off doesn't really feel like a dragon to me. Just simply landing on a rooftop, sitting there, and then flying off also does not feel dragon like.
I literally one time was passing through a smaller town and the dragon landed, looked at me then flew away. It didn't even roar.
Dragons have concentration problems they also tend to hit and then circle before coming back. If they find another target while circling it will usually attack it and might even move on again.
And the circling attacks makes them harder to hit so the attack pattern makes sense, dragon might not know that you heal up while it away

As for runing away, I do that to if loots of people shoot arrows at me

But yes it's annoying then the dragon runs away with 10% health but I have killed many who was busy fighting beers.
As for dragons attacking towns, save before fast traveling.