The game makes a buncha mistakes that could be glossed over in previous games, namely the persona compendium, but since you have 16 slots for personas and 16 characters, you don't have any room to keep spares for fusion fodder nor can you keep a set strategy for all your party memebers constantly. The lack of scape goat personas is noticable here and the system only letting you bring up certain skills chosen based on the personas used and the compatibility is a step backwards from SMT IV and 4 Golden. It heavily restricts what I can use and in doing so ruins a lot of possible synergy in my party. Not being able to hold extras like in Persona 2 and 1, by leaving then with Igor, Margaret, I think was something they should have had in. You can't swap personas mid-fight anymore, though, which I think was smart with the combat direction, but that also feeds into restricting your party's options. The game really needed more persona slots.
The skill card system, while returning, doesn't help as much since personas level up noticably slower than characters, instead of being the character's level. This means that grinding for skill cards is even more difficult to keep in a decent level range and the skill cards are still based on the persona itself, not you selecting which move you'd like to take from it. Yes this is understandable why they do it like that, but because of this, and the enormous price it takes to get the skill card, it becomes taxing and monotonous to get skill cards to get the setups I want permanently seated on a character.
Honestly I like Zen, but Rei annoys me. She's epitomizes many of my story issues with the game. Her jokes are all one-note. Food pun food pun food pun food pun food pun. That's all she really spouts aside from needing to be told how things work and the whole romance with Zen thing. In the game, a lot of the jokes come as references to the games. You got a ton of jokes poking at Yukiko's laughing fits and Chie's love of meat, and almost too many of Teddie jumping in to score with the girls that they start to stop it. There are some good and unique jokes in there, but entirety of the P4 side seems to drown itself in reminding us that these were ppl from Persona 4, instead of playing off their character more.
The P3 cast fairs a lot better with fairly accurate characters and actual interactions, as well as their personalities rubbing well with the P4 cast once those start happening. Though, they totally screwed up Akihiko. The cool-headed fighter who was focused on his training to better himself and save others? The man who loved fights but understood restraint as part of a group? That guy is gone. Instead we get an even more ridiculous and protein-loving version of the Persona 4 Arena Akihiko. And it's really sad, cause it drowns out a lot of the interactions with Shinjiro, who finally gets to get a lot of time to interact with everyone, and I feel they did him well. Y'know, when he isn't being dragged off every 3 lines to deal with Akihiko.
In combat, Downs and All-Out-Attacks being random is stupid. Utterly stupid. While you can increase or guarantee AOA by downing all your enemies and/or getting your full party to Boost Mode, a new mechanic, you can't guarantee downs. Binds are ok. They're a bit annoying and the rate for them at times is ridiculously low, but its nothing completely game destroying. The combat, actually, overall was quite well done. The only real killer is the down changes, since it then encourages using weaknesses to go into boost mode, which makes your next skill cost nothing, in order to use one of your really powerful attacks, instead of using weaknesses to slow the opponent down or get an advantage over them. It makes the game a bit repetitive since then everyone but status effect, buff/debuff and insta kill users would just use 'low cost skill A' to then be able to throw out 'high power skill B' with no cost.