Gameplay. Gameplay was quite good. I like the way you copy the guitar hero even you didn't copy it well. Plenty of circles would make it hard especially that the wc3 can't handle it. It is quite delay when I play it and that makes it bad but I still consider.
Terrain. Terrain was good enough for a mini game. You should change the background. There are plenty of modern models here in the hive or other site. You just have to find it to have a better terrain. It doesn't look good because your playing a modern game but the terrain sucks. Make it more highly appealing to people. Oh my, I forgot, I consider it to good points because it's a mini game
Design. I like the design of your map. Complete of sets like the minimap, preview and loading screen, Keep it up!

Management. I don't see any bugs but the wc3 is quite delay by using keyboards. Plenty of circles sending make it hard and it makes the game too hard and make the player don't play it.
Tips. Put some tips in the quest log to make new players play it easily and more enjoyable. In-game text tips and Tutorials on the quest log would be better.