If quests arent going to be a hard requirement for the dungeon then I think it's fair that actually having done the quests gives a serious reward, not something you can just ignore. Something akin to reputation in gwd2 increasing drop rates, that way people dont have to do the quests but people who have get an actual reward for following the story.
Edit: Before you comment "mandatory" or "forced" please look at those definitions in context of what I've suggested. You will almost certainly find you are using them incorrectly.
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