Its true that Ninja and Sage were nerfed a bit but all the other classes got a bit of a boost. They tried to re-balance the classes in the DS version cause they were trying to make it so you have more options for how to set up your party so you don't have to resort to using the Ninja/Sage team.

I don't think the dungeon themselves are hard but I do give CoD props for being one of the nastiest bosses in the series if not in RPGs in general. That said, I find the boss battle always seems to go one way. Either CoD royally kicks your ass and you spend the majority of the fight trying desperately to survive only to finally get taken out by its signature attack; or you walk in there and bitch slap them back into the void without breaking a sweat

Here's a tip for you if this is your first time through the game. If you decide to level grind, switch to the Black Belts as they give you a huge boost to your hp and are the only real means of getting max hp which will help greatly.