I know this is tricky, and likely controversial. It may also be technically difficult to implement. Having said that, it seems like this would remedy some of the end reward imbalances.
There are nine different groups of "quality" items:
2) Greater Bane weapons
3) Stat damaging weapons
4) Mithral Armor
6) High Skill boost items
7) High Stat boost items
8) Greater X Resist cloaks/shields, Greater False Life Items
9) Potency/Magi/Spell Pen scepters
Right now, everyone seems to be given options from the subset of these 9 that they qualify to use. Melee types, in general, seem to get all of these types of items as choices, while clerics get few choices from the top list, arcanes get few from the uber weapons or armor list, etc. Thus, they miss out on most of the uber weapons.
There's a couple of ways to remedy this:
1) Reduce the number of slots on the end reward option list for melee types - instead of 8 items to choose from, they get 5.
2) Adjust probabilities:
a) Adjust the probabilities so that tomes fall more often for arcanes and/or less often for melee
b) Adjust the probabilies so that greater bane and stat damaging weapons fall more often for rogues and clerics
c) Same with Mithral
Maybe rogues already get good drops, and this approach isn't necessary for them. But that's a side point. The main point is to try to ensure that each class or class group has something of value to trade to others in other class groups.