I just want to say that I really wish 14 had been more like 11v2 rather than what they did with the races and some mobs resembling 11.
I know I'm preaching to the choir by posting here but 11 really was a helluva game. Here's where I think it could have improved
More quests - I loved the party grind. I really did but the game could have used a little bit more for quests. Missions were alright but quests in the game were kind of cheesy, few and far between. I liked the rate at which you exp'd (before it was nerf'd, and even then it wasn't as fast as WoW or RIFT. Still, it took time and effort to level. I liked it.).
Real Guilds - I loved being able to be a member of multiple guilds but in FFXI they were only chat channels *and* they took up inventory spots. They should have been fleshed out with guild calendars, at least. Guild banks and guild housing would have been nice as well.
Inventory - The job system made inventory a precious commodity.
Crafting in FFXI was unique but not enough was really certainly known. Also, progression through 50+ of any craft was pretty difficult. High end crafters controlled the markets and shut others out deliberately. Perhaps they do this in many games but FFXI made it difficult to fight through.
Joke drop rates - Some of the HNM's with their 0.1% drop rates--not funny.
I'm of course not saying it needed precisely the same classes or same abilities. The subjob system has always been my favorite class system and I wish they would have found a way to retain that. FFXI was done right in a lot of ways - I would have been ok with a sequel simply correcting and enhancing 11.
Unrelated, I'd always hoped 14 would have had a character reader for 11 that allowed you to set up statues of your 11 characters in an MH style setup in whatever gear they had. (The gear wouldn't be useable in 14, or even obtainable, but on display. Similar to 11's mannequins.)
Spec'ing properly is a gateway drug.
12 Million People have been meter spammed in heroics.