So I just finished testing the alpha, and I thought it was good for the moment but I have a few suggestions :
Chapter 1 : At the end, after you kill the enemy hero, he drops an item. However, because the winning condition for the level was to kill him, you only have a split second to grab the item before the game's over. Maybe you should make it so more time passes before the level ends, or maybe change it so that the orc's death opens a gate that the player has to cross to win so he still has time to grab the item.
Chapter 2 : Maybe it's just because I suck (entirely possible mind you) but I found this level much harder than the previous one. In particular, the red blademaster was wrecking my units and heroes because he was already level 8 (and he could level up to 10!) when my heroes were all low level and I couldn't build higher level NE units than dryads. Maybe you should make him weaker, and block him from getting stronger? Or maybe I'm just terrible so disregard this lol
Also, when you kill the blademaster, he says something like "You may kill me but you'll never beat lord Illidan", implying that he's dead for real but then he can be resurrected like any normal hero and, at then end of the level, he has a similar talk with Akama and Maiev before they actually kill him. I think you should remove the first dialogue and only keep the one at the end.
Finally, the light blue base has an altar but no hero. If the player destroys the altar, lb will try to build another one but still no hero with it.
Interlude 1: One thing I thought was weird is when the grunt brings news to Illidan & friends, he first says that Maiev escaped and only after Illidan asks how it's possible the grunt revealed that Akama betrayed him. I think one of Illidan's generals openly rebelling against him and killing his loyal soldiers would be much more important than a prison break.
So I think you should change it to something like this :
* Grunt : "Lord Illidan, I bring bad news!"
* Illidan : "What is it?"
* Grunt : "Akama and his Ashtongue tribe have betrayed us!
* Illidan : "What are you talking about? Akama wouldn't dare strike against me!"
* Grunt : "He's freed Maiev and the other prisoners and with their help, they've attacked our clans and killed (red BM from previous level)! Now they've allied against you!"
I think it would make more sense that way.
Chapter 3: I don't have much to complain about this one, it was pretty good! Not too easy and not too difficult, it was fun! Although just like in chapter 2, one of the orcs base (yellow, the one near goblin laboratory where you can buy zeps) has an altar but no hero.
Interlude 2: Very minor point, but the last time we saw Vashj in Int1 she was purple, now she is green. Unless there is a teamcolor conflict (and there shouldn't be in an interlude) you should try to be consistent with team color.
Otherwise this is pretty good, so keep up the good work!
