it's a difficult question to answer, maybe because i want it all.
i can only answer by way of what i am creating as i am full of idea's and dont have enough time to do everything
I have a mastered hack and slash for medium level players - its very enjoyable to actively AM, talk to players, take control of bosses, etc. but its also the most difficult set up - i need ppl be of a certain level/restrict higher level skills, it relies on everyone who comes in working together. this is hard to run randomly - much better to find the players before and then launch with just them.
I also have a very high level masterless challenge, this is my favorite as i am designing it so it can just run, players can enter at any time and simply experience it without worrying about missions and acts and whatever. the ambushes and crafted encounters will all reset with time or on other triggers so it can be up for days with no need to look after
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I would love some lore/storytelling but the problem is they are one hit wonders - once a player has been through they wont be back so i wont devote my time to such a thing yet
What we need i think is a good invasion scenario, that can submitted and put in the Pioneer section as perm content, that would be awesome as many people enjoy mass combat.
sorry for not answering your question at all o_o