The optional door won't be triggered if you immediately follow Nanamo to the exit, correct.
It appears that SE, yet again, is unable to deliver a medium difficulty content just right. As I've said in another thread, the boss on criterion could be tone down a notch. An idea that I have is they could increase the pacing and mechanical difficulty for each boss the further in you progress. For example Boss #1 would be like Hydaelyn, Boss #2 like Endsinger, Boss #3 like Barbariccia. This way, a more casual player can farm silver at the first boss if they find next ones too hard; instead of abandoning the content altogether. Of course, to incentivize people clearing the entire dungeon, each subsequent boss drops more Silver. So people who just farm the 1st boss will take longer time to get enough for the rewards.
Agreed. I don't do Savage and most people would say normal tome gear is sufficient for what I do. But gear progression is still something enjoyable for me. I'm sure some people would be open to form a 4-man static for Criterion since it's more accessible and easier to manage compared to 8-man static.
For those who do savage raiding, it's a good alternative to gear alt jobs or mains that have no luck in PF loot.