Was near one of the dragon lairs and found a regular title-less brown dragon that wasn't inherently hostile. I used Dragonrend on it then quickly got it down to about half health then noticed it wasn't attacking me. I stopped and walked up to it and it just stared at me then started running away from me on the ground. I chased it around like this for about 15 minutes and it never tried to attack me even once. I tried healing it and it finally attacked me after its health went up to about 70 percent, but as soon as I got it down below half again, it just started fleeing again. After I killed it, I wasn't able to absorb its soul.

Is this a glitch or is it supposed to happen with weaker dragons when you are at higher levels? It was on a level 53 character with patch 1.07 installed.

I think it's just a glitch.
I've never seen the weaker Dragons act any differently towards me at high levels.
Even Mudcrabs fight to the death.

Maybe he was just having a bad day?