I'll do this too I guess.
Marisa: She kills trash with Asteroid Belt (and occasionally Earth Light Ray) and Master Spark bosses, optionally using concentrate to build her MAG beforehand. Yeah. Is there any other way to use her? If there is I'm not aware of them. She's one of my main trash clearers due to having a lot of SP, though Asteroid Belt's power is kind of petering out lately and Mystia is gradually taking over that role.
Remilia: She does primary tanking for me most of the time and I build her defenses mostly. Due to Curse she's my first go-to person for taking damage. She's so damn fast though which kind of hinders my switching around, but as I rely on DPS more than burst nuking it's not that big of a handicap. Low SPI affinity is occasionally a thorn in the side as well but that's it.
Chen: Switches in when the boss isn't doing anything for a while and hits stuff. Also kills fast and frail things before they can do stuff to my party in random encounters. Yeah. Again, if there's another way to use Chen I'm not aware of them. She really does do a lot of damage, but I have to be extra careful about taking hits with her which is kind of annoying.
Alice: A general use damager. She's my primary attacker against any boss not resistant to FIR (and there are a lot of bosses that are weak to it), and assists trash clearing too (although her speed is kind of underaverage in my party). She really isn't excelling in any area, but her single target damage is really good and she doesn't fall over too easily either, so she's pretty reliable.
Wriggle: She has the best unbuffed defensive stats in my party, but lacks the ability to raise them by herself like Remi does. I use her as a backup tank when I need two of them or when Remi needs to be pulled out to perserve health. The nice thing about her is that she really isn't weak to anything; her status resistances are consistently good, and her affinity weaknesses are easily patched up with a Holy Mist Robe. She took most of the hits against Eientei for me, and I suspect I'll get more mileage out of her than Remi against Yuyuko too (since Remi's natural SPI affinity is low).
Sanae: I gave her more SKP than anyone else in my party in an effort to make her decent. She had a lot of SP issues early on, but now she can stay in a bit more comfortably and throw out heals more reliably as well. Had to give her some MAG investments to make sure her heal actually delivers, but mostly I've been still building her up for MND. Her heal is flat out worse than Minoriko's for me, as I perfer to pre-emptively protect against status than to heal it away, and with her being the only healer in my team she sadly has little time to throw out Miracle Fruit, although I do like it when I do manage to use it on someone.
Mokou: She's one of my trash clearers, and an auxillary hit taker against bosses as well. Mostly she takes a similar role in my party as Alice does, but she sacrifices a little bit of damage for more hit taking power and speed (against trash). Yeah, her damage looks kind of lackluster at first, but FIR is an excellent element to hit things with, so in reality she still holds up pretty easily.
Suika: Occasionally I have her help out on trash clearing, but she's really kind of terrible at it. Against bosses I ended up using her more to try and debuff SPD than to hit things with Throwing Atlas, but she does a pretty good job at it to be honest. She also has the best magic taking power without buffs in my party, which is helpful occasionally.
Maribel: She occaisonally helps out on trash clearing as well, but her skill costs are too prohibitive. She's excellent against bosses, though, due to self-buff and CQB having small delay and fairly low SP cost, as well as debuffing ability. Too bad SPI is a rather bad element against bosses (it's excellent against mobs though, but then her SP...). Her WND nuke did a lot of damage on Tenshi, so I imagine it will come in handy against Triomagen and Rinnosuke's NTR form as well.
Utsuho: I try to find some safe time for her to launch a couple of uncontrolled nuclear reaction, bring her back out to recover SP, then back out again to nuke stuff. At least, that's my plan, but what end up happening usually is that the boss gets taken down before Okuu gets enough SP back to do anything due to her terrible SP recovery rate. Giga Flare could've been handy against Tenshi, I guess, but I kind of forgot to use her and ended up doing fine anyways. I've put on the Holy Win I found recently on her to try and rectify her recovery issues, so I'll see how well that works aftewards, I guess.
Mystia: Hands down THE best trash clearer in the game. Midnight Chorus Master's power is unreal, and while 80 SP was kind of expensive early game, I can fire off two of them now. Against bosses I tend to try my luck with PAR most of the time, and mysterious song also got used a few times early on before I got the gears to inoculate against status. She's the only PAR user in my team, so that alone give her a lot of screentime on my team. I don't use Ill-Starred Dive much though, since I already have Chen for non-elemental DPS.
Keine: I built her for DEF and to take hits occasionally, and she also buff things in my party. Lack of MND buff continues to cause sorrow for my team, but for the stats that she can buff, she's pretty reliable now that she has the SP to use them more than a couple of times. Her offensive buff is also occasionally helpful in trash clearing, although with 88 SP cost I can't use it a lot.
EDIT: Since I can't find it anywhere, I went and derived the formula to calculate the SKP needed to reach next skill level: floor(floor(1.25x^2+1.25x)*coefficient), where x is the current skill level and coefficient is an independent value for each character's each stat. The eight characters in the first page have the following coefficients (I'll do the rest tomorrow):
Char HP SP TP ATK DEF MAG MND SPD EVA FIR CLD WND NTR MYS SPI
Reimu 1.2 1 55 1 2 1.1 0.95 2 2 4.5 4.5 4.5 4.5 12 3
Marisa 1.8 1 51 2.4 2.2 0.8 1.1 1.5 1 5 5 5 5 3.8 10
Remilia 1.2 1.5 45 0.78 1.1 1.8 1.8 2 2.4 4 4 4 4 10 12
Sakuya 1.04 1.04 40 1.04 1.8 1.04 1.8 2 1.32 6 6 6 6 6 6
Patchy 2.8 0.8 66 3.6 3 0.8 0.8 2.88 2.88 3.8 3.8 3.8 3.8 3.8 3.8
Chen 1.28 0.8 35 0.98 1.4 3 2.4 0.6 0.6 7 7 7 7 5.5 5.5
Meiling 0.88 2.4 35 1 0.9 3 1 2.6 1.4 4.5 4.5 4.5 4.5 4.5 4.5
Cirno 1.2 1.2 40 1.2 1.2 1.2 1.2 1.2 1.2 9 2.8 3.8 3.8 7 7
I don't know how helpful this is, but hey.
