The game is too maxed out, or being not balance in a way it will be replayability or game-oriented, my team wouldn't last long to those 3rd or 4th wave unless we were given items or some gear to strengthen us ahead on the enemy waves. The idea of the map should be hero arena and warcraft 3 related.
Terrain is lacking too much, just tiles and cliffs and trees making uo a maze look for the map, that is not a good practice. Somehow this kind of idea is fitting for practice but not meant for an actual output for play, although you gave in some honorable hero offense you can do better.