The current state of random loot is disappointing. And not just because they haven't restored or finished the prefix/suffix list since the ghostbane debacle, but rather because there really isn't any possibility of anything dropping of value compared to named loot. Under the current (ML?) system, I don't believe this is fixable, with named loot being way underpowered compared to named loot. If we tried to remedy this with more powerful prefixes/suffixes, we would just create the opposite problem - loot that is too strong relative to named loot.
My proposed loot generator would work as follows. All loot would have the usual 4 attributes, 3 guaranteed and one possible.
1. The +
2. The prefix
3. The suffix
4. The extra property
Rather than determine a weapons ML based on chest, and then filling 1-3 to reach that power, which creates a uniform power level for that loot, each of the attributes should be rolled on separately based on Gaussian distributions around the middle value. For example, let's say you pull a khopesh from a ML 30 chest.
1. From Gaussian distribution centred at +10 for chest level 30 you could get a "lucky" roll and the weapon is a +15
Chest level would merely affect the chance of this happening, maybe 0.5% for a level 30 chest and 2% for a level 35 chest, for example
2. From full list of random prefixes, "holy" prefix is selected. Lets say there are 10 potential versions of that, eg. holy I, holy II, holy III, holy burst, etc...
Again, Gaussian distribution around the middle prefix for level 30 chests, with probabilities to "better" prefixes as chest level increases.
3. From full list of random suffixes, "evil outsider bane" suffix is selected. Again, let's say there are multiple levels of "bane": lesser bane, bane, greater bane, sovereign bane, epic bane
4. Possibility of an extra weapon attribute eg. metalline, silver, cold iron, etc. For example, probability of one of these for level 30 chest could be 10%, for level 35 chest could be 15%
Anyway, under this system a +15 silver holy X khopesh of epic evil outsider bane would be possible, although statistically incredibly rare, more rare than any named loot. What is important is that the ultimate levels along any prefix or suffix line would have to be selected such that they are of appropriate power. For many of the current prefix and suffix lines I'm not sure that the current "best possibility" is sufficiently powerful - greater bane is an example of that (with even the "epic bane" seen on some named loot perhaps not being powerful enough on a weapon limited to 4 attributes max?).