I just finished windspear, loving every second of it. After deciding to finish up the beast quest, I headed to the temple ruins, to go after Mazzy. After progressing through a rather easy (but very interesting) dungeon, I come face to face with the shadow dragon. On the Firkaag high, I expected an epic battle. However, after about 20 seconds of my paladin and other fighters beating up on him with the Carsomyr +5, he went down without any problems. Anyone else feel this way? Maybe I should do it at a lower level on my second playthrough...

Yeah, you should have probably headed to the temple ruins first. The enemies you encounter in the game are set at a certain level, and if you wait too long to go somewhere, you may vastly outclass them. In your adventures outside of Athkatla, you were probably meant to head to Trademeet, then De'Arnisse Keep, the Shadow Temple, and then Windspear hills.

Wow my order was messed up. Here is how I went:
Keep (had some trouble with the golems)
Windspear Hills
Temple Ruins
and now I'm heading to trademeet. I guess it will be a piece of cake.

Temple ruins were the first place I went ouside of Athkatla. Little more of a challenge early, but I think it's still the easiest dragon.

On a side note, if you overlevel enough, you'll find a lich (or two? can't remember) in the ruins. Yay.