I think you guys are looking at this as too much of a direct translation of the game. Just look at the difference between WC3 and WoW. WC3 has a good number of different units, but WoW has only 9 different classes that have a huge number of abilities. I mean, you could say that warriors are like foot soldiers or grunts, but since when did grunts have abilities like cleave or sunder armor? Off the top of my head, I can't think of a single unit in WC3 that is dedicated to healing, but in WoW you have 1 pure healer and 3 classes that have healing abilities.

So I doubt that you're going to see the exact same classes in a SC MMO that you do in SC itself.