Well, playability is average to average low. Reason is mostly the map is very badly balanced both as defender than attacker. You can immediatly see as defender and very hard you have no reason to fear a defeat, and as attacker and easy you have no hope to win. It immediatly break playability, execpt perhaps for fan of easy victory : play this map as defender in this case.
Balance : 1
Impossible as attacker, except at easy using advanced option.
Impossible to loose, even at very hard as defender.
Creativity : 3 no real comment to do. Perhaps could I rate it 4 as average, so it's difficult 18 month after the game came to surprise the player and give something new.
Map design : 4 nothing stunning, but efforts are visibles. I have to concede that work it timeless in a small map.
Story insturction : 2 a bit limited but exist. One the average low however.
Played in V1.2. First attempt attacker at normal : immediat stop of the game. Second defender very hard : very easy victory. Thrid attacker easy, using advanced option : victory, fourth : attacker normal using advanced option : failure.
Well my Lord, I usually never use advanced option, except if the mapmaker say it's a valid option. Here my only hope to beat your map was to play (as attacker) at easy and use advanced option. Perhaps more skilled players than me could beat the map at easy, or normal using advanced option. But point you have not enough money to buid siege engins as attacker except shields.
As defender : no way to loose.
I can suggest you to test your maps, yourself, both as attacker and defender, to detect balance problems. If these problems have no solution, in your feeling, balance your map only for defender, or only for attacker, and warning player of this.