What confuses me in your words is:
After that, I calmly built up my army and cleared the area.
For example, here is my result:
http://i47.tinypic.com/1zpjkle.png
On easy difficulty.
It took me 63 in-game days.
This map can definitely be completed faster.
We could compete on a harder difficulty level. :)
Then we can conclude whether it's the weakest map or not...