I gave this level a high playability score because I had no problem playing it. The scenario itself was way to short and way to easy. You might want to camera cut to your unit, not the Heka Gigantes. You might be able to make a short cinimatic in the begining just to show the Heka.
There was no balance in this scenario. All you had to do was go through simple quests for giants and fight the Heka, who you could defeat no matter what. You might want to make the Heka stronger and put some more fightable units in the map itself.
I thought that putting a Heka Gigates as the main enemy was good, but you should add somemore aspects to your scenario, such as stated above, put more enemies or develop a bit more storyline.
Map Design: 2
Your map design was one of your weakest areas. I was a bit confused why Achilles' home village is in the middle of the Underworld, and you didn't put much work into terrain mixing. You could have added more embellishment to the map, as well as including more of the map as well, not just one fourth of it.
I was confused at first even where my guy was which could have been fixed with a short cinimatic, as said above. Also, I only knew what to do by reading your text on the download page, so you should definently put instructions into your scenario. Also, you should have developed your story a bit more then just saying a Heka has destroyed Achilles' homeland and he is setting out to kill the Heka.
This was overall not a horrible scenario. This is just learning in the process of becoming a master map designer, and just remeber, all great designers started out in your position, so just keep trying.