I enjoyed playing your scenario for about 30 minutes, there were no bugs or trigger problems and I did alright on most parts. Just btw I didn't go all the way till the end but only one team remained.(the poison team)
When I was fighting a couple AI it was balanced, I would attack them 2 or 3 times and then I would win, they would retaliate a lot and they would help their allies and it was quite balanced and it took a while to kill the blood thorn team.
The story was ok, it could have been more creative, there was no cinematic and no quests so it was very simple, but simple is sometimes good and in this case it was alright. Next time add more features like unexpected events, talking, a cinematic etc...
Map Design: 3
The terrain was good and the trees and all were fine but there wasn't a lot of eye candy and the forts were merely normal cities behind walls, with no playing with altitude etc...
As I said the story could have been more deep and the instructions were fine no confusion there, just try to capitalize and watch the grammar in the objectives, it looks more professional.
I tried o be as harsh as I can so next time there is improvements but I enjoyed your scenario and it kept me busy for a little while.