I haven't read all of the posts here, but reading a few I will say that I am one of those that have played from the start and am a casual player, especially as I have an often busy job. I do have a DA (I had been playing AQ and started DF in testing and fell in love so got a DA as soon as it was available), and I do have about half of the calendar classes so those do make things easier for me. I am casual and so do not like to grind and farm and so have only done so on rare occasions, and that is why even though I am one of the originally players and haven not stopped playing I am not even level 80.
I am a player that likes to do everything and try every release and so when the Inn first came out I was struggling and battling, doing my best to try and beat them, looking at all strategies on the forum, etc. After a while I had to accept that they were for the players that do like to spend hours trying everything out to beat the boss, that had spent so long they were max level, etc. and so I have put the challenges aside and don't feel bad about not completing them. I am hoping though that the Inn guide on the forums keeps getting updated so that I can go back and beat all of the challenges, hopefully when I am level 80 rather than needing max level.
For the story quests I have found a couple hard and requiring a few tries, but none I think were too bad and I thought the occasional slightly difficult challenge (only slightly, not Inn level) was good for the story as Verly said before. However as Verly said there is a difference in power between DA and non-DA and then I also have some calendar classes so that can make it easier for me.
Throughout the staff for DF I have always thought it a fantastic game. At Uni I had to stop playing AE for a couple weeks for exams (AQ, DF, MQ and AQW), and when I started again I only started playing DF and AQW again (it was a real shame giving up AQ and MQ because they were such great games in their own ways as well, and also now knowing that MQ would stop and so if I could have kept going for a few more years I could have enjoyed all of its story).
Someone pointed out treating DF like a VN and I agree, it has such a great and also with some stronger classes I can just go straight through the base enemies to then enjoy the cutscenes, maybe having a little harder time with the boss because of extra mechanics that then means if you specialise in taking out base monsters you would have more difficulty and so you then need to change classes and balance.
Like others I want to say how great the team is doing on DF. Tomix/Dove with his great artwork and stories. Verly with some good, interesting mechanics, not necessarily making boss fights hard but all the different mechanics being added to the game, as well as support with different story ideas. All the rest of the team with ideas for their own storylines, their artwork they add, and also support in the main and side storylines.