Improve the loot / downgrade the difficulty of simple maps. Yes, needed. (It is sad when a VE map is easier than a 50s simple map with the same group...just one person level 60 to dig them. Further, the loot is better.)
A new map tier in the D/VD/ED range, I don't think it is needed. In the D/VD range, you have tier 1/2 raiding. In the VD/ED range, you have tier 2+.
The issue is probably that people want a new "6 person group" map tier that is capable by only highly tiered characters where high end competition doesn't exist so much in zones with better equipment drops.
However, with the above said, a new "groupable" map tier between VD and ED for high tier equipment people /may/ help in getting these same people from doing AoE pull groups in zones meant for lower tier equiped people. This would also have the effect of these people being able to get more xp since the new area bonus of many map zones wouldn't be negative, as opposed to the bonus in these AoE agro pull zones is.