DDO was converted from a initiative/turn-based-system to one of the most real-time MMOs out there (meaning you literally click the mouse button to swing your weapon, and press a button to block with your shield in real time). While converting DDO to an Everquest/Wow/etc model would have been a moderate change, going real-time completely changed the dynamic of combat.
Enhancements. Sure, they sounded like a great way to customize your character, but D&;D 3rd edition was already the most customizable version yet. All these bonuses did was throw the class balance of D&;D (Balanced over the course of decades), and moreso, the multi-class balance, completely out of whack.
Add in the ease of obtaining magic items, with the small overall pool of magic items (compared the the cannon material) and you have a game that says it is D&;D but plays nothing like it.
I can't comment on role-playing, as I only did it in short spurts and it seemed fine. Then again, RP is about the people, not the game - you can RP in any game out there with the right people.
If someone ever makes the equivalent of a modern Pool of Radiance (the AOL Online Version, not the Console Game), with a semi-turn based MMO engine, I'll buy stock in their company. And no, NWN/NWN2 do not count, as (sadly) they don't work well as MMOs.