Stop dragon attacks
I'm high level and finished the main quest, but my game is unplayable at the moment:
It was said that every dragon fight is something special, why am I spammed with dragons like every 5 minutes then?
I can not do anything in this game anymore, because a new dragon is just waiting for me.
If that would just be out in the wild, ok, but I have 2 dragons raiding Dawnstar, 1 old dragon (not targeting me, but just attacking NPCs) in Whiterun, ...
Tried to kite them out of the city and then using Dragon Fall (they won't land on their own), but that sometimes just results in them flying far away (effect still "active"), just waiting for me to return next time.
How to deal with dragons or play the game without them?
I recently resolved the civil war and one situation was that two dragons wiped a whole camp in 30 seconds.
I've completed the game and all factions with a level 51 Khajiit archer and didn't notice any significant increase in the number of dragon attacks at any particular point in the storyline. I am attacked perhaps once every 2-3 in-game days. In your circumstances, I would suggest adapting your character to deal with the increased attack rate and develop a few evasive procedures. Some ideas:
You already have Dragonrend. By forcing the dragon to land, you are able to kill them more easily or force them to fall behind if you wish to escape.
Take potions of fire and frost resistance to reduce the damage the dragon is able to deal, potions of healing to negate that damage, potions of stamina to help you put distance between yourself and the dragon if necessary, and potions of fortify one-handed/two-handed/archery/destruction to help you deal more damage.
Hire a companion with high health that engages the dragon in melee or ranged combat. Optionally also seek out Shadowmere from the Dark Brotherhood questline. By having one or two tanks to absorb damage and distract the dragon, you will be free to fight or escape at leisure.
Attack the dragon from the side, targeting the wings. The tail attack can stagger you, and the head attack can one-hit kill you. The wings deal less damage comparatively.
If you need to escape, aim to run through a forest or an area with a significant number of large objects covering the ground. The dragon, unable to land, will attempt to deliver one or two aerial attacks before locating the nearest wild animal, hunter or guard and get distracted by it. By using Dragonrend, you can force it to seek an area to land, often a fair distance away.
Sell the dragon bones and scales, or craft armour from them. The profits will offset the cost of fighting the dragons. By accepting the dragon hunter bounties from the local Jarls, you will get extra coin for eliminating dragons and ensuring a dragon-free Skyrim.
As Krazer mentioned in comments, it seems that one way to avoid dragon attacks is to not use fast travel. In various discussions on the Bethesda forums, I've seen a lot of people complaining about the number of dragon attacks and pretty much every one of them starts off with saying that they get attacked every time they fast travel anywhere. At the other extreme, I pretty much never fast travel and I've got a level 56 Khajiit who has faced a total of 21 dragons in 130 hours of play - and that includes plot-related dragons and dragons sitting on top of word walls. At a guess, I'd say I've seen seven or eight random dragons, tops, and I get in several hours of play between them.