I’ve been periodically skimming the Gamefaqs and Resetera topics for this and have been picking up tips from people who have played the original Vita version.
For the dynamic difficulty and grinding, the game does raise difficulty as you play more battles, but supposedly this incline is not as severe has previous games. Additionally, it does not raise as fast if you fight the same battle over and over (something about your battle rank increasing at 2% if you grind the same battle vs it increasing by 10% by switching battles). So if you’re going to grind, find an elemental mine you need crystals from anyway I guess.
Something I’ve slowly been picking up on via what enemies do to me and what strategies the game incentives with the optional battle rewards is that status effects, Interrupts, and Protect/defense skills are going to become the heart of the combat system. Nessa (the starting rogue) was not very appealing to me and I didn’t see myself using her much at all until she built up that toolset full of debuffs. One boss I could do very little physical damage to (like 6-20 HP) but using poison it was taking 178 damage every turn! She’s also got both a ranged attack and a sleep attack for quelling conditionals, and an interrupt for disrupting turn order. She’s the best.
Using sleep and paralysis seem awfully important to manage the large horde of enemies. With Beatrice’s club I’ve got Bonecrusher to cause ATK down and Seismic Strike that can interrupt and potentially cause paralysis to all ground-based enemies. Ogniana’s axe has Maim for Speed down and Vertical Smash for Defense down, both of which make a much larger difference than in other games. And one time I was about to lose the game when she suddenly sparked Dimensional Break, an AOE that caused instant death on all enemies.
Mondo can cause Poison with Mizuchi and it’s also a ranged attack for quelling conditionals. Zigor has ranged attacks, Paralysis, and Confusion so far, and his Quick Knock generally pulls him to the front of the entire timeline. Jamto has an Atk down with Optical Slash and a counter with Optical Slash.
Protects, Counters, Interrupts, and using Defense (just not assigning an action on a turn make that character Defend) are things I’m still trying to learn how to use but they seem like they can be powerful. It seems like each Protect or Counter skill only works with a specific type of attack (slash, pierce, or blunt) but I’m not sure if this is signaled in your movelist? Or if you need to try it out and remember it? But Jamto’s Optical Slash does a ton of damage and negates any damage he would have gotten (maybe you can put him in the center of the Phoenix Dance formation?). Pulling off Protects negates damage for a particular character by the Protecting character performs a block, meaning they don’t take full damage either. This sounds very useful for harder battles.
For Formations, I too have found Royal Hearts to be the old faithful. It’s clearly designed as the stable average formation, but I’ve been experimenting with the others on Easy encounters. One thing I noticed is that the other formations have multiple Benisons that can activate on conditions other than “you’re close to losing” like Royal Hearts, so that’s one benefit they can have. I’ve been using Free For All on some of the harder battles because it increases speed and my characters have been lagging behind recently (those Succubi are too dang fast). Momentun is good when you’re in a battle that has some weak foes and you have reliable and versatile damage dealers because you get 2 BP every time the front two characters kill an enemy. It caps at 11 BP while Royal Hearts is just 8, so in the right battles you can establish a strong BP pool.
All For One has 5-11 BP and increases on United Attacks, which means you need to make specific kinds of kills to increase your BP, but it has three Benisons including Asamas’ Strength, which boosts your attack when you’re fighting strong enemies. Petalstorm has 5-7 (!) BP and increases on any kill, but it has two benisons such as Bartlett’s Strategem which causes defense down, speed down, and chance of sleep on all enemies during protracted battles. So those Benisons can be a bit more practical than the ones Royal Hearts provides, and could maybe even make a large difference depending on what you’re up against?
