I will try to be as unbiased as possible. These are my opinions and experiences, so if you care to read OP, or anyone else, I am not trying to change the game to cater to only myself. I actually have no concrete suggestions that are long thought out. I will just throw out ideas and share what I think about this game.
I have been playing actively since April 2014. So I have a year and 3 months playing FF14. In that time I grew to love this game. The only other MMO I have ever played in my life is DC Universe online. In my time playing FF14, I made cool friends, met assholes, played various battle classes/jobs, raided, etc. The only thing I have not delved into is crafting/gathering (yet). I loved most things about this game. Then came Heavensward.
The story, new huge areas, flight, new job skills, excitement of new dungeons, new gear (some re-skins that are available to more jobs), made me so happy and giddy. Shortly after I beat the story, I started hunting and looking for new statics to be raid ready. As soon as this happened, I started to enjoy the game a lot less, and see what I actually didn't like about ARR. It hit me like a truck. I was now doing the same shit as before. I was failing at hunts (even in a party actively hunting, I would miss A's and S ranks. People were relentless on my server with early pulls), and I was grinding tomestones (Myth, Soldiery, Poetics) in order to gear up again so that I can run EX primals for a weapon (like Shiva's Diamond weapons), to then raid. Huh, felt familiar. Let's see hunts still blows (grinding for new sands, oil) and the only time hunts were awesome were in patch 2.4 I believe, basically the patch when most were not hunting anymore, I don't remember which). Law is Darklight 2.0, and I was in a rush to be at the top again. It felt so awful that I decided to become a "casual". I decided to play at my own pace, I decided to stop hardcore raiding.
I admit, it stung hard seeing people with Hive weapons and max geared while I wasn't. My competitive nature urged me to do the same shit again, but playing the story at my own pace made me see how free I was playing. People in my LS and free company were farming Ravana EX by like the 3rd day of early access. Now I see how SE played it real safe. No I am not calling them lazy. I know they worked their asses off, but I already got through the best part of the expansion in my eyes. Soon we will get a new Crystal Tower, Syrcus Tower, World of Darkness with more of the same formula, and a new relic weapon to go through hell with. There is no real fundamental change.
What can they do? I honestly don't know seeing how my MMO experience is limited. Perhaps like a base defense/horde mode? Open world PVP? Further character customization? 2man dungeons? (Like DCUO duos mode and no not overgeared lv unsync), raids that involve environmental interactions? (No not just pressing 1 button to active a shield like in Leviathan EX or Bismarck), I really don't know. I can't really put my finger on it, but take away the shiny wrapping paper, and 3.0 is more of 2.X. This is why I will have a different approach to playing because it works for me. I can only suggest the awesome things I loved in DCUO, but that MMO is vastly different. SE said it themselves that ARR was more about building a foundation. Now is the time to gamble with new ideas. Do I really want to go through 3.X and then do the same in 4.X?