Hello!
It is a little late to talk about it for me, but some days ago I met the problem I said in the title, the 2 dragons near the word of power didn't spawn at all. At that time I didn' care about that because I thought I was in the wrong place, so I went on, completing the Dawnguard quest and going on with other quets I met in Skyrim. But now, I'm curious about what was the problem. Obviously I've returned back today, but nothing happened as I expected.
I've passed too many hours to go back and redo everything again, so, what have I missed? Was there something very important to loot from those dragons? Or I have just missed an epic batle?