As a very experienced CRPG player, I agree with the OP that the "normal" difficulty is harder than most CRPGs. According to eRe4s3r's post, this was also the consensus of the beta testers, but it was too late to make significant changes.
Part of the difficulty is the "bootstrap" issue. If you are a level 1 character in a dungeon of all level 10 monsters, there is no way to win. You need some mechanism to provide foes close in level to the player at the beginning of the game for the player to gain experience and some levels so he can survive in the (virtual) real world. One example is the catacombs under Aleroth at the beginning of Divine Divinity. Most CRPGs have something similar, like the low level monsters near Seyda Neen in Morrowind or the valley of dragon flies in Might & Magic 7(?). The tutorial dungeon does provide guidance in general game play, but doesn't have the monsters to serve as a bootstrap.
I believe there are ways that this could be improved, and hopefully will, in future patches. For example, the dungeon under the abandoned General Store could be expanded greatly in terms of battle opportunities for low level characters to gain experience.
It seems to me that the current difficulty level is unfortunate as there are so many excellent things about Original Sin. The flexibility of casting a pool of water then casting an electric spell to electrify it or a fire spell to make a steam cloud is reminiscent of the original Dues Ex--very challenging to implement, but a lot of fun to play.
