If you want to progress in making maps, you'll probably need to read this :
http://jeffkillian.com/NUMA.htm
I see many problems in Cross of Fire :
At first, you have the mine problem : the bigger amount of objet you add, the longest the map loads. So try to have very few objects in maps. Here, you don't need the mines on the ceilings, and if you just don't want to allow the player to fall down in the bottom of the rooms, just be sure he cannot climb back : this way, he'll try not to fall, to end the level.

Second thing : the gameplay : all the 4 rooms are based on the same 'gameplay' : a block guarded by two drones.
Once you got one room, you have the same thing to do 4 times... Try to be more inventive, or people won't just want to finish up the map.
They are many tricks N can do, try to make people enjoy doing them ! :)
I won't rate this very map, as I think you can improve.