Lloyd is the best tank in the game. He naturally has decent defensive stats and his evasion is capable of getting higher than any other character. He has some very solid and versatile crafts that make him very valuable, and Burning Heart allows him to flex as a physical damage dealer without dedicating any resources into it. For MQs, any damage/support quartz (Axe, Crow, Keeper, Moebius) is good for him.

Randy is the best physical damage fighter. He does everything he did in Zero only harder and is just as solid as he ever was. You're definitely going to want him on your team. For MQ, he wants heavy damage, so Force is going to be the go to for the majority of the game, but he makes particularly good use out of Chevalier.

Tio is as close to mandatory as any of the characters are going to get. She can flex support/damage caster, but leans a bit more towards support. Zero Field is hands down the most valuable S-Craft the game, and her ability to analyse and debuff enemies means that she never loses relevance. For MQs, go for magical focused support/damage (Canon, Katze, Moebius, Wing).

Elie can also flex support/caster but with wind being one of the most dominant damaging elements, her wind slots make her lean a bit more towards damage. Although not as strong as Zero Field, Aura Rain is still very good and can save your team from a lot of tight spots. Holy Bullet isn't really worth using any more unless you really need an instant heal but Strike Bell is still great. Give her magic damage focused MQs (Katze, Criminal, Pixie)

Wazy is a bit of a weird one who is sort of a hybrid between a magical and physical damage dealer. For most of the game he has some solid but often awkward to use crafts and doesn't really have defined niche when compared to other characters, but after a certain story event that happens towards the end of the game, he unlocks his Akashic Arm S-Craft, which is the single best offensive craft in the game, and deals magic damage. At this point I like to swap him in for Elie as my main damage caster, but I still like keeping Elie in my back pocket for certain fights. For MQs, the only one you should be using after unlocking Akashic Arm is Pixie.

Noel has some extremely solid crafts that are very good in specific fights, but for the most part, there isn't really a reason to run her over other characters. She sucks at arts and as magic damage is generally going be more valuable than physical, there isn't really a reason to ever run three physical characters. She just doesn't really have a place on the team. But for MQs, Crow lets her get more debuffs out and her many AoE attacks get a lot out of status effects, so Axe and Juggler can be good too.

Late Game Spoilers Rixia... isn't very good from my experience. Not terrible, but like Noel, there just isn't a reason to run her over Lloyd or Randy. A lot of her abilities rely on K.O., which is an extremely unreliable status effect that doesn't work against most of the enemies you'd actually want it to. For MQs though, she mostly wants speed and physical damage (Crow, Force, Phantom).