The phenomenon you're experiencing is termed 'power creep' - and it happens in essentially all MMORPG. Over time, the accumulation of slightly imbalanced concepts in the game create a massively imbalanced scenario.

Much of the problem in DDO derives from the design decision to make it a 'casual-friendly' game. No matter how foolishly you play or uncoordinated your group is, you can always eventually finish any bit of content with enough gear (whether bought from the store or AH).

This is very, very different from more 'hardcore' games. Even if you give a bunch of average players the same gear access as an 'uber guild' in such games, those players will simply be unable to complete the content because they lack the degree of skill and coordination as the 'uber guilders'.

So in the same way DDO eliminates any sort of 'elite' that has access to content others lack the ability to complete, the average player in DDO can take a look at truly abysmal players and note that the game doesn't really penalize them for their incompetence.