What makes a good solo farming area?

This thread is not for identifying good areas in themselves, I am more interested in discussing why the identified areas are good, and whether we can use these criteria to locate other good ones.

It seems to me that the main characteristics of a good farming area (Prophets griffons, Nebo/nkp ettins, droks trolls, hydras, grawls) are:
- close to an outpost (don't spend lots of time running back and forth, or waste skill bar slots just to get you past "non- cash crop" enemies)
- predictable and consistent enemies. The more you know what you will get, the more you will be able to design a build that will allow you to counter it easily. Most of the areas above only have 2-3 types of enemies that deal similar types of damage.
- potential for valuable loot

That being said, it seems to me that most of the popular farming areas focus on melee type enemies. Is this because they are easy to counter with various 55 type builds/ stances? Or are the farmers of other types of areas just better at keeping their areas secret?

Just as an example, I was recently trying to find a place to farm glittering dust. Tried the undead outside Bergon Hot Springs, but I was only coming up with 20-30 piles of dust for my 20 minutes or so of trouble. This doesn't seem to be worth it, and would thus fail the consistency of drops test. Farming overfarmed griffons at 1k per run produces like 90 piles in 10 minutes. So I would say this is not a good area for that purpose.

Any thoughts on additional criteria, or unusual spots that might meet these?

The reason being for melee enemies would be because they'll surround you right away. If an enemy has a ranged attack, it's not going to walk up in front of you and attack. When these areas were first discovered, Balthazar's Aura, Zealot's Fire, etc.. all combined would make quick work of enemies that would gather around you. SOJ can work for ranged enemies I suppose for those trying to farm a new area.

high level monsters with limited skills. The griffons were great for farming because they're lvl 2(2~4? can't remember), yet they only had melee skills. A hardy warrior w/ enchantments can dish them out easily. If you know the skills the mobs use, and you can prevent them and deal damage at the same time, you got a farming area.

One other trick: Having skill at selling the results for good prices. E.g., I discovered a healthy market for submaximum fire and blood wands, and farmed _____ heavily to great profit.

And, of course, areas with little or no Mesmers and other interrupters