I love Dorothea, and am considering it for a future daughter. She would be named after my fiance's grandmother, who was also Dorothy.We would call her Thea, though.
I agree, it's very nice on its own; however, I think it's a bit nicknamey and would rather have a longer and more "formal" name from which I could derive the nickname. Besides, I think Dorothea is absolutely great and would love to use it.