The more I think about it, the more I think all of these concepts (camping, infrequent/unique loot, slow leveling, disparate level ranges within zones) MUST go hand-in-hand with each other if they have any chance of accomplishing their objective of re-creating a legacy feel.
They tend to go together because they strengthen similar goals.
Let's say, your goal is that people should try to group up whenever they have the time (and don't feel too anti-social that day). You can't have a game where you can't solo anymore, but that does not mean you shouldn't have a massive carrot for grouping.
That gives you two sub-goals:
- Make desirable long-term (in play session time) groups
- Make easy to build a group
Making desirable means that your most desirable game items must come from groups; you can't have solo activities rewarding the best whatever.
Making desirable means you need a group to get to your target; you can't have people simply showing up at the target, grouping to take it down, and then leaving. That gives you the WoW named zergs or the Rift autogroup, which aren't groups. Which means that elite targets are deep in elite areas, those elite trash mobs WILL kill you, and either you have dozens of trash groups to fight, or fewer groups but with slower/longer combat.
Saying "will kill you" means: they will pursue you until at least your potential destination, and you can't shake them by dropping them on an unsuspecting player/group on your path. Oh, and overlevling the mobs should not be a get out of trouble card; lower level mobs should still be challenging/deadly, at least until you very significantly overlevel and overgear them.
Then you make easy to build a group; which means that it should be very common to find all the roles required for a group (that implies sharply defined classes are out; you need to have your players switch between tank, heal, buff, debuff, CC relatively easily and AS the group builds up).
Grouping should be wide, which means you should be able to group up across a large range of levels/gear levels. Which, thankfully, is also a goal you got from previously: the power curve should be relatively shallow, and people over level should find challenging to tacle those mobs, and people underlevel should be able to significantly contribute (and not miss 80% of the time 3 levels above them).
Which, in turn, implies that over-leveled people should also find something rewarding from the mobs their group target.
So, from that simple goal: "people should form long-term groups in outdoor areas", you get:
- Shallow power curve
- Slower combat
- Large elite outdoor areas (possibly 2/3rd of a zone at the high end) along solo-friendly XP/materials farming areas
- Long leashes
- Slower/random reward: mobs are not always up and have larger loot tables
- Ease of adapting to different roles (which does not simply include "toggle spec", but also means similar gear for all roles, and a lower bar of difficulty to perform a role you're not familiar with, at least in non-extreme environments)