Because I am a bit OCD, if I were in charge of DDO I would update some of the old and outdated aspects of the game.
- Spell lists, especially the Cleric, Ranger and Paladin spell lists need to be updated. Example: Most of the second tier pallie spells are made obsolete by equipment. Example 2: Rangers get 2 offensive spells that are DC-based but have few means or reasons to raise their spell DCs.
- Ship buffs need an update, the House K and House D ship buffs both give 1 DR, for instance, and these sources of DR do not stack.
- Favor rewards should be revised to be made more useful. Note that the final tier of The Twelve favor gives nothing, and Free Agents favor is only useful to characters that can make traps. Also, I'm not sure how useful the "extended spells" given by House J and the Church of the Silver Flame are.
On a separate but related note to the first point, Clerics need Domains, in some form or another so that they can add new spells to their spell lists. Otherwise there isn't much reason to play a Cleric over an FvS without that added versatitilty that a Cleric brings. I would suggest a few basic PrEs/trees that all clerics would be able to choose from: Offensive casting (choose an element, maybe?), Melee/War and Healing/Support. These would be in addition to whatever PrEs/trees that race and/or faith give access to.