I'm of the opinion that the Dragons are actually really well done. Yes, they are predictable, and if you powergame, they're a pretty big joke, even on the highest difficulty, but that's fine. I still find myself just enjoying seeing them on screen, they look so good, and move so well (Most of the time).
One point of interest though, Dragons are actually
very infrequent encounters for me, I'm not exactly sure why, but I can go hours upon hours of game time without ever seeing one. If i'm not actively seeking one out, my rate is about one every six hours. My friends however, see them at every turn, I think one of them has killed 29 outside the College of Winterhold alone. The only exotica about my games that I can say, is that I've never fast traveled outside of extremely infrequent occurences, such as bug checking or just going on wholesale slaughter with no intent to save. Maybe they're on a timer based on the actual days in the game.
I'd certainly welcome harder dragons though. They need more attacks that are faster, but less powerful. For the most part (On Master Difficulty) a Dragon of equal or greater level has the ability to kill you in one or two attacks, however those attacks are very easy to avoid. All breath attacks can be negated by a ward, and it's slow chomp attack from the front can be dodged fairly easily. They needed some weaker, but quicker attacks, simlar to the wing swipes, in order to bring themselves to a level that poses some risk. A few AI tweaks, such as the dragon using it's breath attack while walking backwards (Which they already do in some cases) could also help.