So basically if you want a higher % chance at legendaries you need to farm act 4 because that when you'll have the most amount of NV stacks. More incentive to farm act 4 which is fun, but I feel even more pigeon holed into my "freedom of choice" with this option.
Agreed, that shouldn't happen.
One alternative/solution could be to make the quests and exploration progress "free-roaming". So you could do everything in whatever order you wanted to. Still only one time however, until next reset.
Such as start with act 2 and clear a few areas there, jump to act 4 and clear up to Diablo, and then back to act 2 and clear some other areas. Free-roaming only available after you achieved that quest progress on your character before of course, as in no jumping to act 4 before killing Azmodan once on inferno etc.
Also, NV stack shouldn't be so high that you would only reach it near the end of a full playthrough.
In MrMonstrosity's example you could reach it "reasonably quickly" on higher MP.
Shouldn't lose stacks over time tbh. And no stacks lost on log out.
Make us choose when to reset the NV stack.
"Simply" (probably not that simple) prevent enemy respawn on enemies you already killed, even if you relog.
That way you have two choices:
1) Move to other areas.
Gives you a very good reason for exploring, to get the very most of your NV buff.
And a good reason to start your game in act 1 and play all the way to Diablo, even if it is over many sessions.
2) Reset your current game progress by picking another quest in the menu screen (pretty much like you can do now for quest bosses).
You can do that after you cleared the game 100%, or whenever you want before that point. 5 minute farm runs would still work for those who want it (would just be less effective due to the high NV stack count).
However, all NV is lost when resetting your quest progress.
So you cant farm the same area over and over without resetting the NV each time (like today).
Would by far be my preferred solution.
I like Bagstones idea about extra boss drops the more you cleared as well.
Like X% of mobs (or just elites/named) cleared in an act = X% MF bonus at the act boss (multiplicative MF) or something like that.
Rare spawn mobs and side-quests should have higher droprates as well. And the mini-bosses related to them be more interesting.
MrMonstrositys idea of rare crafting mats from named mobs would be quite nice as well, and further incentivize exploration.
Tbh, I dont think you can encourage exploration too much.
So god damn more fun if the whole game is open to you, and worth it to go through, than knowing that 5% of it is the most effective (wherever those % might be at any given time)
Only skimmed the post (its pretty damn long!) but looks like many interesting and good ideas in there.
Especially the NV system, which has been a pet-peeve of mine. Mostly agreeing with your concept and goals for NV.
NV has the potential to solve a lot of issues all in one.
Would prefer if the NV buff could remain between sessions however, as to not hurt short gameplay sessions too much.
It is difficult to make such a solution un-exploitable though. It would basically require that ALL killed monsters stay dead between sessions too. Until quest progression is reset.
It would make it much more reasonable for people to play through all acts and kill everything to get a high NV stack, if they could do so over multiple sessions. Then when everything was dead in their current game - or just as much as they wanted to clear - they could reset everything.
In general, add more bonus rewards for doing those sorts of "full playthroughs" (more rewards from doing the main and side-quests, exploration and finding rare mobs, killing the bosses etc). Short, effective routes are kinda boring. The solution should be to make it more (or at least equally) effective to clear/explore everything and do the quests.