No trust me, I get your complaint, I really do.
It's just... stupid, to say the least.
As SFJake already pointed out, you're completely exaggerating this whole "3 games" deal.
You do realize that if they had mashed all 3 races into one game, the development length and costs would have skyrocketed, yes?
Not only that, but with gaming advancing as it is, the game would have looked like shit when it came out, unless of course it underwent an engine overhaul during the development process, which would have further increased costs and length.
I fail to see why only having a campaign for one race qualifies it as an incomplete game.
Let's take Modern Warfare, for example...
Did the other enemy factions get a campaign?
SWEET FUCKING JESUS, THE GAME'S INCOMPLETE!!!
I just don't see the disadvantage in having a great story stretched out over 3 normal sized campaigns, even if they hyped up the size of the campaign.
Hype aside, we're still getting 3 normal sized games, at 3 normal prices, which are essentially 2 normal expansions.
We've had expansions in previous Blizzard titles, but this time there are two.