I am the map author. I am surprised that anyone plays there. It's quite huge for 1v1. I think it suits more for 2v2. That said, I'd rather make the mainland a bit smaller (and remove gems). Let me know if you'd be interested in these changes.
I dont think so - Mammoths are fine as is. what you must consider is that a Mammoth is only 2000$. There is no unit which gives more punch for the buck.
They allmost allways kill more that they are worth. Thats why you can grind down the enemy with unending waves of mammoths and inf for added damage and rocket soldier removal.
A key point though, is to get a lot of warfactorys (3+) for this to work relieably
They didn't seem to do so hot this game. They are extremely slow. I'm pretty sure they aren't much more efficient than heavy or medium tanks (if at all). Arties+infantry will wreck mammoths+infantry. For such a high tech and "iconic" unit, they are seldom built (in great numbers at least) by "pro" players.
(Originating form some other game hinted at in my Smurf ^^)
The map is "duel island".
hf