I really don't understand why they didn't do the Doom of Valyria...
I think GRRM doesn't want to ever explain what actually happened there.
I'm guessing the immense time skips between episodes is a feature? Do they want to go all the way to the mad king?
My impression is that we're still essentially watching a prologue. We're seeing the pieces set up for the succession criss when the current king dies. I think once we get to that point time will flow more like it did in GoT.