"it isn't a very good curve."
If the game was murderously hard from the off then a lot of people who only want to log on and kill sprites for 20 minutes would have been driven away. People who have been driven away don't buy expansions. So instead they put in a system where even the most casual player gets to see and kill Diablo but the hardcore gamers would still have something to aim for.
The mistake Blizzard made was in having it take three trips through the game before you reached the level cap. I agree this was a bad decision and it did drive people away simply because it got tedious. But you're blaming Blizzard because you didn't die during the tutorial, and that's silly.
As of patch 2.0 this week it's all moot anyway - monsters now scale to your level and difficulty levels can be adjusted on the fly so you can pick one that's right for you. If you play a brand new character on Expert (the second difficulty level) you should get to 60 by the time you complete Act IV for the first time, and loot rains down upon you like pigeon crap in Trafalgar Square. If you've already paid for the game, you might want to give it another go.