I just so happen to own the Prima Guide for Skyrim and I thought I'd share with you all the enemies that level with you! I've already spoiler'd the only enemy that I feel may spoil your experiences in Skyrim, so don't worry about spoilers! So without further ado, here they are:

• Hunters
  
• Hold (any hold) Guards
  
• Imperial Soldier
  
• Fort Commander (Imperial)
  
• Imperial Legate
  
• Imperial General
  
• Stormcloak Soldier
  
• Fort Commander (Stormcloak)
  
• Stormcloak Commander
  
• Stormcloak General
  
• Alduin

I'm pretty sure dragons level with you, or id be 1 shotting them right now...

They don't. And anyways if you search youtube, you can find Dragon one shot videos

so how come it still takes as much effort to kill them at lvl 39 on my 2h warrior as it did back when he was lvl 13 when i started the main quest

Are you fighting different breeds?

You have different types of dragons and they can be level 10, 20, 30, 40, or 50. That's probably why.

Well, isn't that sort of the same thing? Sure you're not fighting "Bandit"s anymore, but unless you're really nitpicky, isn't a fort full of "Bandit Chief"s pretty much exactly the same?

And at low levels you always run into dragons that you can fight. Sure, the basic dragon doesn't get any more powerful, but you don't care much that there's a single spawnpoint left for a dragon you can kill in two hits when elder dragons are shoving their spiny backsides up your corset.

Sort of the same as what?

As fighting a dungeon full of normal bandits...they fight just the same, the only difference is they're tougher and drop a bit more gold.

Well bandits and bandit chiefs are separate npcs with their own respective levels. As the game goes on you will probably see more bandit chiefs than you saw in the beginning but still plenty of bandits.