I for one did download the map.
I added a couple of heroes (making red team a player) and ran around the map in the game. This gives me a better idea of what we are looking at in game mode.
I include a game screen shot as attachment.
As a general rule of thumb you should show screen shots from the direction and angle that you will be using in the game. If you have cinematic sequences then get your views from the cameras. If you are getting player views then put it in game camera view or test the map and take snapshots from inside the game - it puts things in perspective.
The first thing you will notice is that the game view is very small segment of the map at any given time. The next is that your lowest angle does not show the horizon at all. Further Black Mask and Fog of War have a large impact on the game image. I scrolled my camera in the game to the lowest angle to get as close to the images you provided.
In this context things like the waterfalls will not be seen in all of their glory - and your wide beaches become very empty in the game due to what little you can see from camera angle. The Central beaches are especially empty in the game - perhaps more shells and washed up debris? half buried logs, stones or something.
BTW that tree of ages is phase shifted - it appears that the units can run through it.
Also units will have an impact on the landscape - you know animals like frogs, skinks whatever.
Its a pity you do not consider yourself good at terraining, for this game you appear to be right on track - very few needs for this map exist.
It appears it would work as is for a cinematic as well as the game with minor changes or none at all.
