So I've been playing for 6 hours so far, Level 8 Nord, just wandering around the wilderness mostly. Found a few cool little hidden dungeons.

Ho, what is this? The 'Sightless Pit' eh? Alright let's have a look.

I enter the dungeon (it looked like a hole in the ground), find some monster thing that almost kills me but I manage to take it out (barely). Suddenly two more attack and I'm killed in about 5 seconds. No matter what I do there is no combination of weapons, armour or spells currently available to me since they kill about half my total health per hit. I even tried spending all of my perks in armour/blocking (I hadn't spent any at this stage) just to try it out. Did nothing to help at all.

Lo and behold the way back is blocked (apparently since I jumped into a hole to get into the dungeon the exit is now a mile above me, floating in the sky, taunting me). I have no way to exit this dungeon that I quite literally cannot get past the first few monsters. My last save game before that was a fair while ago and would be seriously irritating to have to go back to.

Am I missing something here? Are there dungeons in this game that are just way too powerful to complete? I have not had any significant trouble whatsoever up until this point. There was no warning that this was a dangerous dungeon or ... anything at all.

This has seriously bummed me out of what was until now a really great experience. Am I doing something wrong? Or is my mistake not quicksaving every 37 seconds? Is this a bug in the game that I cannot choose to exit?

Yup. There are areas of much higher level that you. I'm lvl 11, Nord, and I encountered my first 'Draugr Death Lord' or something. It kills me in like 3 hits and has only about 10000 freaking health. I had to run away. Now, I am playing on Adept (3/5) difficulty. What are you on? Perhaps cranking it down to novice may help you get out? But only to a point. You may have just wandered into a bad area and are going to have a tough time getting out. D: