The fact that we got to play a demo of Final Fantasy XV, even though realistically the game is probably another year away, feels almost surreal. So with that said, the demo is not that indicative of the final product. A lot of things might actually change, though some core concepts will certainly remain.
So it might seem strange that I'm already nitpicking about a game that might go through rigorous changes, but it's not out of the question for games to release with numerous problems. After putting in a considerable amount of hours into the demo, even past actually finishing it, I think the game has a lot going for it, but there are some things that Tabata and his team might want to work on, or change slightly for the better.
Graphical optimization
This is easily the weakest argument here, since it is after all a demo. While the graphics seem fantastic, the game does take frequent dips in framerate.
It's not terrible when exploring the massive map, but it's bad when it happens during battles. Especially once you level up enough and the game decides to keep dropping Magitek soldiers in droves, it not only makes the game look worse, but it also makes the battles a lot more difficult.
Like I said, this is going to easily be one of the first things addressed, so I'm not worried, but I felt the need to point it out.
More coherent combat
The combat in Final Fantasy XV is easily one of the game's highlights, at least in the demo. It's fast and frantic, and when fighting a few enemies at once, manageable and quite strategic. Having to balance when to attack and when to dodge is a pretty great system.
However the whole thing falls apart when the game decides to drop 10 Magitek soldiers on top of you, while you're already fighting six big monsters. It becomes crazy unmanageable. It becomes less of trying to manage attacking and defending, and puts a much higher emphasis on strictly dodging. And since dodging costs MP, you'll soon lose the ability to dodge altogether, meaning you're overrun and out of luck.
Maybe this was the design choice though. Perhaps you're supposed to run from unwinnable circumstances.
Stamina system?
While sprinting, you occasionally run out of breath, meaning Noctis stops to catch his breath until he can move again. While it makes sense that a person would have to stop after a bit of heavy sprinting, there is no meter that shows what your stamina is. And while I understand having stamina makes it so you can't simply keep running away from monsters non-stop, it would make more sense if stamina was tied down to strictly combat. With areas being as large as they are, it seems strange to limit the player's ability to always run from place to place. And even more so since there is no bar signifying how much stamina you actually have.
Gambit System
Even though there are four people in your party, you actually only ever control Noctis. Your other party members act on their own, and for the most part, do a pretty good job. However, there needs to be some form of giving your party members orders, or at least giving them a general ruleset like in Final Fantasy XII.
Given how hard the Behemoth boss is, it would have made more sense if you could set certain characters to focus on healing, and others on debuff spells to ensure we could do more damage.
Locking on
While the camera system isn't that bad, it gets worse when you lock-on to an enemy. What's worse, the lock-on mechanic itself is somewhat wonky.
For one, when you first try to lock-on, it doesn't always stick. It only sticks after perform an attack on it, or after you press R3. A lot of times this caused my camera to constantly spin around as it tried to lock-on to different enemies since it didn't initially stick.
Friends healing and resurrecting
When Noctis gets in his downed state, his party members can bring him back up. However, the problem with that is they don't always do it in a timely manner. While I understand that it's probably done to ramp up difficulty, it's still very inconsistent.
It's even stranger when Noctis is down and one or two of his party members are huddled around him, but aren't actively reviving him. Sometimes it gets to the point where enemies will actually get between Noctis and his friends, even though they've been huddled around his for the past 10 seconds.
It's one of those mechanics that aren't transparent enough. Do you have to just wait it out? Does it get triggered by something?
Over reliance on Summons
One of the coolest aspects of the Episode Duscae demo was the ability to get Ramuh as a summon. As amazing as his summon animation actually is, it's an easy crutch to rely on. Can't beat that Behemoth? Summon Ramuh and he'll one shot him. Can't deal with those Magitek soldiers? Ramuh! Getting overrun by the pack of beasts? RAMUH! There doesn't seem to be any sort of resource cost to use him outside of having 0HP. Sure, the tradeoff here was that you get no EXP and no Gil, but even then, Summons seem to powerful to simply rely on them to beat any boss.
Final Fantasy Type-0 had an amazing trade off where it actually killed off one of your party members. And while many could simply say that there are 13 other members you could play as, the fact is that you're losing a member that you've been relying on. Not only that, the Summons weren't that powerful, as in they couldn't one-shot an enemy boss. I hope that Final Fantasy XV has some sort of good trade off as well.