They're great, but could be better.
Basic dragons suffer from the "leveling syndrome" and even if they're challenging on Master, bears/sabrecats and other non-leveled creatures are harder and own them @ lower levels.
Starting from Frost dragons, things change and they become harder and more powerful, killing giants and wildlife (and me

) with ease.
Anyway, as I say, they could be better so I'm currently planning a mod for when the CK comes out...