I saw this in my contacts on Flickr. It is very much like the cloud in your drought render.
http://www.flickr.com/photos/shotoftheday/4880513324/sizes/o/in/contacts/
It was taken by micfitz
Thanks Henry :)
This nearly perfectly shows what I was after.
The scattering is impossible in TG2 and so is the (darn) glow, not to mention the billow shapes :)
If TG2 (or TG3?) could ever get the lighting as it is in clouds in nature, nothing could match it. Clouds seems to have a world of light physics of their own.