@ ShadowPriest: If having to organize 25 people is the reason that 25 mans have better loot, why does anyone but the raid leader (and class/role leaders, etc.) benefit from that? If your job is just to show up, you didn't put in any more effort showing up to a 25 mand than to a 10 man.

While making the two tiers have the same loot might lower play of 25 mans, I feel like, at least in T7, the opposite happened. Naxx/Sarth/Archavon 25 were so easily puggable that there was no reason to do 10 man. If you didn't know what you were doing, you could get carried through Naxx 25, die on every fight, and come out with a few best in slot epics. In 10 man, it's much harder to carry people, assuming the people doing the carrying are actually in 10 man gear.

The solution, to me, is to maintain the gear disparity, but lower it. Instead of having gear be a full tier (13 itemlevels) apart, they should be somewhere around 7. I think this would keep people in 25 mans for the slightly better loot, while not making 10 man raiders feel screwed for (at least in T7) completing the harder content.