one-handed style is very niche in deadfire compared to poe1. and that niche is not focus generation, you are tanking your focus generation unfortunately (for more info on the niche, i wrote it up in one of the sidebars here: https://gamefaqs.gamespot.com/pc/227477-pillars-of-eternity-ii-deadfire/faqs/76599/weapon-styles). two weapon style is overall best for dps/focus, two-handed style is also good and has other advantages (quarterstaff and pike give you reach like in poe1 so you have good dps/focus while being relatively safe like a ranged attacker if you have a good tank to body block).
with party support a club will work best. also, the cipher doesn't need to use a club, you can have someone more melee-capable use a club to keep enemy will low. ciphers will actualy suffer with club because of the -25% damage penalty from the modal. eventually you get a high-level passive that you can take that gives you bonus to accuracy vs will which will help. edit: same thing goes with morningstar modal. put it on a front-line tank, hit an enemy with it, and suddenly you have a juicy target for a cipher disintegrate.
IMO the tier 1 beam spell is always good although the targeting can be a bit challenging.
ascendant is not really meant for front-loading powers, since you have to build it up. there are other ways to super charge focus generation for an ascendant (there's a unique blunderbuss that can be enchanted with a once/encounter massive push back attack that will top you off with focus almost assuredly). aside from psion, the other ciphers will do overall better with front-loading attacks, and the beguiler can generate tons of focus real fast with the right powers.
i think those are decent stats. unfortunately a cipher on hard/potd is just going to be squishy for a melee-er, you don't have survivability-boosting abilities/passives compared to martials and heavy armor is really taxing on your ability to use powers; so additional con/res may help a bit but won't help the big picture that much. eventually by mid/mid-late game with more powers, the ability to pick up Tough, and the slowdown of the AR vs PEN arms race on hard/potd will make things easier. in the meantime, rely on your party to support you.
firearms are great. their #1 feature is that while reloading, you can do switch to doin anything else, like quaffing a potion, using a power, etc. one-handed pistol with modal is also a super way to do firearms w/ basically minimal reload time (the math works out heavily in your favor doing one-hand pistol with modal that it doesn't with any other weapon). crossbows/arbalests are similar, but they especially come with utility for interruptions, which is more important than any damage they can do.
there are also some frankly stupidly good unique firearms. there's a pistol that can do raw damage and be enchanted to do even more damage on top. there are two blunderbusses that instead of firing 4 bullets, fire one bullet that explodes (also decent for focus generation). there's an arquebus that lets you fire twice before reloading--basically eliminating the slow reload tax.
that's kinda what i do. i give each character a main skill to focus on, maybe two tops. the diminishing returns on party assist are pretty nasty. more important for watcher to focus because there are lots of checks that are watcher-only, but that's the general idea.
the main argument for not giving everyone these skills is that IME keeping your characters stocked with enough potions and scrolls is expensive. eventually by late game you'll be overflowing with high-powered scrolls (through forgotten sanctum dlc) but good potions will always be hard to keep up. I max out at two characters investing in those skills at a time. similar with explosives, though explosives are honstly easier to keep stocked up (most explosives recipes give you more than one bomb/craft, and even really basic ones are good).
in terms of potions being usable by all, the best benefit from alchemy to me is making even lesser health potions extremely useful. combat is slower than in poe1 so drug durations won't get too high relative to fights, but high alchemy is needed if you want to do more than one fight (+ some exploration) with the effects of a drug. edit: also if you are interested in poisons maxing out alchemy is basically mandatory for them to be usable at all on hard/potd. on potd you also need additional help from items and miscellaneous general buffs (like a source of aware to get graze->hit or independent accuracy bonuses not tied to perception).
athletics is also good for a lot of characters. it falls off quickly, but even with the fall off it's very useful heal. i have a fighter mainchar right now that is maxxing athletics (for an item that gives you -% recovery based on athletics), and at level 12 i can heal ~200 health with athletics (at fast speed with no recovery). for mercenaries i might need i tend to pick up laborer as a background since that's +2 athletics off the bat, and that's basically a free, no-recovery potion every encounter.
if you hover over your character, there's a tooltip to the top left of hte screen by default. There should be a number next to a "Concentration" label near the top of that tooltip that will have a number if you have more than one layer of concentration. Plus I think there's "Concentration" next to whatever effect is granting it in the list of active effects. edit: there's also a visual indicaiton in the above-your-head combat short tooltips - the circle that shows your current action will be glowing if you have any concentration. very important for at-a-glance info on whether that enemy caster is interruptible.