People love playing DDO, even with the bugs and problems, and in spite of a few gimped classes. It's a fact. Your formula works! Congratulations on that. However...
Once you get people to buy into the game, you have enough content to keep them occupied for, let's call it 'x' before a large enough majority becomes bored. We will call this the 'Burnout Factor.'
Burnout is a problem all activities have. It's unavoidable that eventually people will tire of your product and move on.
In DDO, you delayed some burnout by allowing people to start over with bonuses ala reincarnation. You added classes and races as well. But the one thing you've done that has significantly stalled burnout is increasing the level cap and adding content to match.
CONTENT IS KING.
The problem is, the more adventures required for the character to advance to the next level (or parallel advancement in ED's) the more variety the player needs to maintain interest. MotU added quite a bit of content, but the expansions following have not. People are suffering burnout. Epicifying old content does very little to relieve this burnout. Only new content, or radically changed previous content has the OOMPH that is needed to forestall total burnout.
If you triple or quadruple the amount of quests from 20-28+ with most of it being new or radically altered content, you will reap the benefits of a more stable player base, more versatile character builds (especially if these adventures are stocked properly with unusual and exotic equipment) and more general player contentment.
Yes, you will get the perfectionists that want every bug to be quashed, but this is an unrealistic expectation of any software run on a server for public consumption. You will also have the people who want the core of the game expanded. While they have valid arguments for, this can be handled in parallel to expansion.
In the end, I support the aggressive expansion of the game world. The longevity of this game depends on it.
(apologies for the hasty writing--I am being pressured by someone to abandon my computer--I will revise this entry later today--have a good day!)