I'm lvl 35 and ended up in dragon territory (somewhere mid-East in the grasslands).

I was on a low hilltop and he landed right in front of me. I went up to him and used Dual Wield Savagery on his face and he died in about 5 seconds. No magic and no companion help.

My theory is that he was a regular dragon, but it kind of seemed like I was supposed to fight him earlier in the game before I got to such a high lvl, but then again, I thought enemies are supposed to change difficulty according to your lvl.

The weak enemies don't vanish like they do in oblivion.

And I'm not even an Orc, I'm an Altmer.

They do. Fighting the basic dragon is very easy past level 15 (but they are rare), blood dragons are a little better. Ancient and elder dragons have a lot more health.

Cool story bro.

There are weaker dragons. There was one near whiterun that I killed when I hit level 50 ... It was normal dragon.

I just had 2 Blood Dragons in a row near Arcwind Point. Cost me all my health potions, luckily a Draugr Wight and his skeleton army helped me.