I'm not really into the whole end game thing (I only did Dynamis once, only went through Nyzul to get to floor 100, went to Sky and Sea only for the story fights/look around/farm Kindred Crests for the later Limit Breaks, etc. in XI and only did what dungeons I had to for my AF in XIV) but I would love areas unlocked by stroyline progress especially if they are amazing and/or unique looking. I agree that the feeeling of accomplishment when I finally got those areas was one of my favourite experiences in XI.