I understand some of the complaints against OB, but I don't really fully agree with any of them, I think a lot of them are made by whiney MW [censored] or trolls just wanting to flame OB.
Go through the Dark Brotherhood and Thieves Guild as an assassin character. Then go do the main quest. You'll HAVE to lower the difficulty to the minimum, even at Kvatch. The game balance is incredibly broken. I stopped playing countless of times my character because the game told me I had to be a warrior one who constantly level up his combat skills. But I am an assassin, I upgrade sneak, security, short blades, archery, alchemy. So the more I levelled up, the weaker I got. I'm wondering how I'll be able to get through the main quest and then Shivering Isles... And then add artifacts which aren't real artifacts, and other problems. There's a difference between not agreeing with someone, and ignoring game breaking flaws. Even Todd Howard admitted the level system wasn't ideal.