It's perfectly fine. Check out Herbie Helm's site as builds his own lugs in this same method. His lugs will blow your mind. I love this one piece head lug.

Check out his Flickr page as Herbie posts up quite a few photos of his customer builds step by step. Page 13 gives a nice group of shots of his custom lugs from tig welded to fillet brazed and overall form cut out.
http://www.flickr.com/photos/helmcycles/page13/
Helmcycles.com