Yeah I think it's bugged. What's worse is, I've seen dragons that not only ignored me, but
fled from me! This was after the main quest for me and I had Dragonrend, and it didn't work. In particular this was during the civil war quest; I'd chosen the Imperial side, and this dragon was hanging out near the camp. No matter what I did, this mongrel fled, but because he was in the area, I couldn't fast-travel. I spent 15 minutes trying to get close to this dragon and he kept flying off. I even got frustrated and tried to console cheat to fly to him, and he still flew away (and then the game crashed). Some dragons aren't meant to be kill-able, perhaps?
Before some of the patches, I've seen:
- Invisible dragons (nope, I'm not on a PS3; I'm on a PC)
- a skeleton dragon (and not the one in the tomb)
- Dragons flying backwards
- Dragons flying after they were killed because it was scripted that they would take off from their perch (I saw this on Youtube)