Naxxramas

[lemekim]

3) Balance.  The effect of gear post level cap is simply astounding.  Blizzard cannot balance *anything* anymore, really, since the gap between epiced-out raiders and non-raiding 60's is so immense.
-Bolty
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I think there is a little wiggle room for items that can be obtained from such instances. Specifically, the items can be specifically tailored and balanced to the needs of that class. For example, if the instance is designed for a warrior/rogue, the final boss can drop a bow/gun/crossbow that can have less DPS then regular weapon, but more stats, and the stats can be distributed more evenly to provide the biggest boost possible within that item budget. Similarly, this instance could be the source of wand that are better boosters of stats instead of being higher DPS. And Druids/Shamans/Paladins could get their relics there as well.

Or it could be the source of a belt enchant for various classes.

Yes, you still would have to design the instance for each class (or at least for groups of classes - melee, casters, healers), but the item balance can be resolved through other means.