A number of the issues raised could and probably should be addressed together. Otherwise you end up with a bunch of random mechanics like Dismantling and Bounties, which aren’t quite good enough to stand alone. You could solve a few things together.
Trash mobs not worth it
Nemeses require hunting
End game lacks a sense of motivation
The idea of “threat meter” has been brought up before- basically if you kill mobs in a faction quickly in succession, the meter rises. It could have a few tiers where it may release a pack of tough trash mobs and eventually releasing the Nemesis when you’ve killed enough. This makes more sense because the player drives a type of rubberband AI. Lore-wise, if you’re killing the faction’s dudes at an abnormal rate, then they’d start sending out the specialists to take down the threat. Killing trash mobs becomes important because there aren’t enough Heroes to sustain the threat meter alone. Tie the ceiling of the threat meter to the reputation tiers and it’s vaguely scalable from start to end.
Now that could satisfy players for a while, but this is a loot-based RPG so in my mind you’d have to tie gear in as well. The idea of enemy faction-specific loot would fit it nicely. Similar to friendly faction gear, the enemy factions could drop certain tiers of blueprints, armor, augments, etc once you reach the according reputation level. The extra wrinkle would be to only allow these drops when you kill enemies at the top of the threat meter. This motivates players to enter areas with a high density trash mob area to farm for items. With a few Legendaries like the Outcast’s hood, that’s plenty of incentive.
Bounties serve no purpose once reputation is maxed
Scrap/Dynamite/Iron are worthless
The idea of Skeleton Keys is an interesting mechanic that could be recycled. Once you reach max Rep with a friendly faction you could unlock faction-specific side areas, similar to Hargate’s Isle, but with more variety. Basically, it could be a stronghold of the faction’s worst enemies with great mob density. Maybe even tie it to the impending Survival Mode. However, restrict access to the areas with debris/bridges with high costs that reset each time. If all that’s keeping the Bane of the Bane of Cairn away, then you’d damn well believe they’re going to move rocks in the way to block you. It may even be worthwhile to create a blueprint that requires a lot of resources, including rare components that only drop from enemy factions once they reach the top tier of the threat meter.
So now you have to give a good reason for players to want to enter these strongholds. Max rep bounties could begin offering MUCH better rewards, but make the quest require access to these new areas. I’m not sure what the rewards should look like however. Legendaries is the obvious answer, but as others have pointed out that makes no sense lore-wise and it diminishes motivation to kill enemies to find Legendaries. What could work would be a new type zone-exclusive item. Maybe not even gear. My half thought-out idea is a material similar to Ancient Hearts that enable Blueprints to a shiny Augment that works on Relics. And instead of making generic bonuses like +100 OA, you could imbue them with build-defining skills/item procs that are like those on Legendaries, such as Blood Orb’s 100% Elemental conversion to
Chaos.
At any rate with the latest preview of mod tools, it looks like Crate may be giving us the keys to solve the end game problem ourselves. I look forward to peeling back the onion!