Ian your post made me laugh. I too sweat heavilly, i'm especially crap in really hot conditions, or even mild conditions for that matter. I break into a sweat even after getting out of a shower!!!
I've often wondered about the high wicking properties of garments, normally as i'm hiking along - sweating like a pig. I've lost count of the number of sweat soaked super light weight high wicking hiking garments I'v used. I suppose, what I can say is that i've noticed they dry more quickly once I hit a breeze and for some of the lighter tshirts, are pleasant when you can feel the breeze through them too.
They are obviously more comfortable than wearing a plastic bag.
Sorry, I can't recommend one that I've had huge success with yet. (Low weight yes, keeping me dry? Errm, No).
I had thought it was because I was the only grossly oversweater there is, but now I know there are two of us. Hurray.
If you find the answer let me know.