I made a post on r/dissidia geared towards compiling feedback on the Closed Beta, so that people can make a co-ordinated effort to address very particular issues with the game via the official feedback pages for the beta. I may as well copy-paste the issues I came up with there for the heck of it:
Network Infrastructure/Online Communications
-Matchmaking takes a long time, most of the time.
-Frame rate lag and input drops/delays are frequent in most matches, in particular I find my inputs for switching targets to drop most often, dunno if that's a specific bug tied to that input or not.
-I've had multiple softlocks while matchmaking. Sometimes it happens before the game has found any opponents. You know it's happened when you press Circle to back out of matchmaking, but it never goes back to the character select screen no matter how long you wait, forcing you to close the application. A similar thing can occur after you have been matched with other players. Normally, the game displays the stage you'll be playing on before it displays your teammates, but sometimes it never displays the stage, it will find you some teammates who you can communicate with while you wait, but since the game forgot to pick a stage, you're stuck there and once again have to close the application.
-IMO, the matchmaking feature itself just doesn't seem to do much to actually match you with players of your rank, or of a similar connection speed. I was encountering Gold A players as early as Bronze C, and my Y'shtola is currently at Silver C IIRC, but I often still get paired up with Bronze E or D players. This can be incredibly frustrating as players at Bronze E or D have probably played less than 10 matches and still haven't figured out how to play the game well. Most of them still try to play it like a 1v1 game so you're stuck trying to pick up their slack, having them never listen to your cries for support, or you're trying to summon but they never help you and then the enemies start trying to intercept you and you have to cancel it. And even if you play well, you still get negative matchmaking points, and if this happens enough, you drop a rank (this only happens in Silver Rank and above too, so the Bronze partners who were lacking in performance don't have anything to lose).
-While the character specific communication quotes are charming and entertaining, some of them are a bit vague and impractical. The one that stands out most is Y'shtola's quote for asking her party members to help her summon: "Let us place our faith in another". She's by far the character I have the most trouble getting a summon off with purely because I'm spamming this quote and nobody seems to listen, and I think it's because of how vague it is - it sounds like a generic "let's support each other!" friendship quote, and not asking your team members to help you summon. Almost every other character has the word "summon" in their equivalent quote so it's clear what you want from your party members. So yeah, in cases like this where character specific communication quotes favour personality over practicality, I think they could use some revision.
-Some animations and hitboxes seem to go screwy when the game is having connection issues, which can make fights get unpredictable. I assume this is just syncing issues, but they can be jarring. Like for example, you hit an opponent with a move that is supposed to send them plummeting to the ground (like Zidane's Up + X Bravery attack in the air), but instead they suddenly fly off into the distance midway through falling, even though nothing hit them on the way down and the game didn't even stutter or anything.
Game Mechanics issues
-The Guard mechanic seems to be one of the biggest points of contention for a lot of players, and I partially agree. Most of the characters are melee-focused characters, so guarding an attack and getting sent flying anyway is really nonsensical as it doesn't allow you to punish the opponent, it still knocks you back as if you weren't guarding and you are still stuck in a degree of hitstun, you just didn't take Bravery damage or give the opponent Bravery. However, I actually think this is fine for characters like Y'shtola, Terra, and Shantotto, who want to be keeping their distance from opponents anyway - they're rewarded for guarding by being sent away from their opponents, which is exactly where they want to be (the magic bubble effect also fits them since they are magic casters). But for melee characters like Cloud and the Warrior of Light, they shouldn't be sent flying when they successfully guard, it should function just as it did in the original Dissidia games where the opponent bounces off and is momentarily stunned, giving you time to counter if you timed your Guard correctly. As for melee characters blocking projectiles, they should simply nullify their effects, or in the case of smaller projectiles, they should be reflected back at the caster, just like in the original Dissidia games. It would make the Guard mechanic far more interesting and rewarding for melee characters to use.
-I think a lot of characters have far too much end lag on their moves, making them more punishable than they ought to be. "Fast" character like Zidane and Lightning feel just as punishable as powerhouse characters like Cloud and Dark Knight Cecil. Overall, the game feels slower than the previous Dissidia games, which is a shame because I think there's a better flow to it with some actions (like how you can now rush opponents into the ground or wall and they don't get immediate iFrames, it only happens after a HP attack or three instances of being wall rushed by Bravery Attacks), and the movement controls feel smoother (at least in offline play, lag makes them feel clunky but that's just lag for you), but characters I used to love playing feel less enjoyable because they're nowhere near as nimble as they used to be, everyone basically feels like how Cloud felt to play in the original games, if not even slower.
-HP attacks feel way too slow in general, resulting in there being very little KO confirm options in the game. They were slow in the original games, but not this slow on average, and they had tighter homing, plus you had those special "Brave Attack to HP Attack" combos that could be unlocked in the original games, as well as the chase mechanic. Here, it seems like the only way to securely snag KOs for most characters is to build your Bravery to beyond 3,500, switch targets immediately, fly over, and try to sneak up on an enemy who's occupied with other teammates. You can wall/ground rush opponents with Bravery attacks and follow-up with an HP attack, but that's a lot more situational, and your opponent can still tech it before they hit the ground. Granted, sneaking up on characters with HP attacks is the intention with some characters, mainly the Assassins, but even most of the Vanguards feel like they don't have very reliable options. I feel like Marksman characters and Specialists pulled the biggest straw regarding HP attacks because some of them are just ridiculously good compared to the melee characters (Firion's Vortex of Arms and Y'shtola's Holy come to mind, and it's for that reason I find them to be two of the more fun characters to play as. Vaan is in a similar boat, since he's entirely designed around using HP attacks almost constantly). Some characters are always going to be better than others in regards to HP attacks but I feel like the gap is far too skewed, at least based on the beta (I know there are already other HP attack options for the beta characters in the arcade version). Some moves, like Lightning's Razor Gale, literally seem non-functional - it's supposed to home in on the enemy, but it's way too loose to hit anything, and it's far too slow to hit at close range most of the time.
-IMO, target switching should go up and down a linear list of your opponents, and not be based on who's physically to the left or right. It's far too difficult to keep track of all of your opponents and where they're at relative to you when the camera focuses on just one opponent at a time, and the game lacks a free camera mode like the original Dissidia games.