Balance and D&D

[Borror0]

I just used the core books and allowed all classes races from them, I didnt buy splat books for 3- and didnt allow anything I didnt own, one player offered to buy me a book if I allowed it I was tempted but in the end didnt do it.

Well, in 3.5 D&D (I only played 3.0 and 3.5), it is/was very common practice to not allow certain spells or classes from non-core books because they were too powerful.

In a PnP games, the DM is the regulator of balance. He is there to ensure everyone is having fun and will balance the adventure so that everyone is having fun, to the best of his capacities. He will try, as much as possible, to make sure everyone feels useful. This means disallowing some classes or spells because it will make someone way more powerful than the others.

DDO is no different, it requires balance.