Sophie no question. We use that exact party (with humans on Pascal and Hubert), and it's extraordinarily powerful. Pascal does all the damage you could ever ask for, Hubert is the best lockdown character ever, and between Cheria and Sophie you have an extremely powerful healing engine. With only Cheria, assuming you're on chaos, she'll do something stupid to get killed and it can leave you in a tough spot. Sophie is an all around versatile character anyway so you really can't go wrong with her. If you have three or four humans or just aren't playing on that high of a difficulty setting, you could definitely get away with Asbel, and human Hubert and Asbel working together will be very hard for a lot of enemies to deal with. I'd really suggest avoiding Malik; if you're using Pascal, what little niche he may have had is pretty obsoleted.
I will say that if you're by yourself, either AI Hubert or Pascal (depending on your choices) will really frustrate you. Those are the two worst AI (especially AI Pascal who just has no concept of how to use her effectively) even though as human controlled characters they're the best two.
dunno what problems everyone has with her. Always serves me well on chaos
but yeah, go for sophie
she will pretty much not die ever (assuming you are doing your job holding some of the enemies or the boss) and heal you whenever you need it.
Hubert set up : Manual, makes him die slower than the AI
Pascal AI set up: I like to do Mostly A artes, 2nd most aggressive AI, rarely defend, turn off the **** B artes (Keep things like cyandine, bloodflame, fearful storm, fangirl dream, and the GROUP HUG IN THE HEAL RING)
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Since we always have Pascal on human it's hard to say her best strategy, but given what I know about how she plays well, you'll want to set her to A-heavy so she stops the stupidest thing she does which is just run straight up to the enemy and start casting a B-arte which is suicide unless Hubert is doing some serious work to cover her (and the AI won't be able to make that judgment call). I don't know if this will convince the AI to actually use her moveset correctly (which is A-arte chain into Flux Form into B-arte), but it has to be better than what she does by default. You'll also want to turn off several of her lesser B-artes like Pyrogenic Ring since honestly she's just throwing away an opportunity to do something worthwhile when she casts something like that (turning off all of them except Cyadine would be worth considering actually). As per her accel setting, you should either set it to 50% (which is usually the best time for Pascal to use her accel since you want it up as often as possible) or don't use and just switch to her to manually direct it. Pascal's accel act is one of your most important party resources if not the single most important one so making sure you're getting powerful use out of it is very important. Since Pascal doesn't have any real healing moves, it's probably safe to set her to defensive just to encourage her to block as much as possible.
As per Hubert, again we haven't explored too much since we use him as a human, but I have an idea that will certainly be worth trying. Try setting him to B-only aggressive with ever B-arte off except Rolling Thunderbolt. If the AI does what I think it will do (just spam Rolling Thunderbolt wildly), it will be a big improvement over usual AI Hubert. Against bosses that can deal with Rolling Thunderbolt well (which isn't many of them), just turn on only his lowest level B-artes so he'll just go nuts with the quick, safe gun shots. This is far from optimum Hubert play of course, but it's probably better than him eiher spamming Healing Wind or charging to his death which are the two main things AI Hubert likes to do left to his own devices.