I've played in and run evil campaigns of various sorts in both 3.5 and 4e (though not 5e, I think my learning will transfer), and run into a lot of problems: My Guy Syndrome comes up a lot, as does a tendency to default to a regular D&D storyline only with more stealing of spoons and kicking of puppies to remind ourselves we're evil. Sometimes an evil campaign instead descends into over-the-top motiveless violence until there's no story at all. There's a whole host of at-the-table and in-the-story issues, and I tried many different strategies to address them. Eventually I came up with a framing device which works well for us in avoiding these problems:
Provide the PCs with a Master to guide them toward orchestrated works of Evil.
Start the game with the PCs as underlings/minions/hirelings/apprentices/etc of a powerful evil NPC. The Master has a complicated Evil Plan and he tasks his minions to enact various parts as the Plan progresses: "Bring me the soul of a hound archon," "Raze the border keep," "Steal the Apocalypse Gem," "Help a spy infiltrate the paladin's ranks," and so forth, tailored to the PCs' abilities.
This provides the party a reason to work together despite having different agendas (and working together will hopefully bond them as friends so that they want to continue as a group) and establishes small achievable evil goals that accumulate into an Epic Evil Event.
All you need to do is ask the players to make sure their characters have a good reason to work for the Master: The serial killer likes having his rampages subsidised (and the Master protects him from the Law); the necromancer seeks to learn from the Master's experience and gain access to his libraries of forbidden lore; the mercenary's in it for the money and benefits.
Eventually the Apprentices will surpass their Master.
Expect the party to betray their Master at some point, hijacking his Evil Plot for their own gain: this is not only expected, but awesome. It's the Master's Evil Plot, not yours, and the story isn't about the Master--it's about his apprentices. Consider the Master to be training wheels for evil, setting an example which the party can then follow to surpass and overthrow their instructor as they level up.
This works because Evil Needs Goals.
As Ed describes so well and AgentPaper elaborates in the D&D context, evil needs concrete reasons motivating its actions. The Master provides goals and motives while the players find their feet in the new paradigm, channeling and guiding their exploration of what it means to be evil in ways compatible with the D&D paradigm without simply kicking puppies during a dungeoncrawl.
A word of warning: Alignment is tricky.
D&D has a history of the details and nature of alignment sparking major heartfelt arguments, because D&D alignments are not easily (or appropriately) matched to real-world philosophies and moralities; they're narrative simplifications to support the game's conceits and draw their power from storytelling conventions rather than from genuine moral complexity. Exactly what this means and how to deal with it are beyond the scope of this answer (and possibly this site, although there's a LOT of questions on the topic you can look at), but you should be aware it exists and be ready to talk with your players about what "Evil campaign" means to them so there aren't nasty surprises mid-game.
For your players' specific choices:
P1 has the right idea by picking a SAD class in the Druid, but has his dump stats off kilter. While dumping Strength, even down to 6, can be managed (especially for a Druid who should be able to travel light, as Druid defensive buffs are excellent and they are well-equipped to not need tons of rations, etal), he shouldn't put his racial +2 into it.
Given his array, I would have him dump Strength and Charisma -- Dexterity is needed for initiative, and Intelligence for skill points, so you can't dump either it turns out. Wild Shape is also more beneficial for P1 than he thinks -- Natural Spell comes at the same level as Wild Shape itself in PF, so he gets casting-while-shaped essentially "for free".
Along with that, he should put that +2 racial bonus into Wisdom and bask in the glow of a +4 starting Wisdom bonus.
P5 is also on the right track with focusing on archery -- the casting of the Ranger is not strong, and with two full Vancian casters in your party (namely, the druid and the wizard), his casting won't be needed for much, while the Dexterity-based skills will be quite useful in a rogue-less party. Furthermore, his choice of Charisma for a dump stat is a reasonable one -- it's not nearly as severe a dump as in P1's case, and many Rangers don't rely upon Handle Animal the way Druids do.
Regarding concerns about healing
Having played a Druid in a party where that was the sole access the party had to healing magic, by the way, I would strongly recommend your party obtain Wands of lesser vigor if you are willing to waive the [evil] descriptor on the spell or Boots of Earth (if Fast Healing 1 is enough) if they aren't, and give one to the druid and one to another character -- Druids can't convert to healing spells as they get Summon Nature's Ally instead, and spell slots are precious especially at lower levels.
In general:
You are right to be somewhat concerned about this...
The more relevant sum in this case is of attribute modifiers -- if it's less than 0, D&D 3.5e (and presumably PF (Pathfinder) as well as it's derived from D&D 3.5e -- if it's not a rule there, you can always port the 3.5e rule to your game as a houserule) has a rule that allows the player to reroll for their stat array.
In your case, it comes out as follows:
- P1: +3, +2, +2, +0, -2, -3 = +2
- P2: +3, +2, +2, +2, +1, -1 = +9
- P3: +3, +2, +2, +1, +1, +0 = +9
- P4: +3, +2, +2, +1, +0, -1 = +7
- P5: +3, +0, +0, +0, +0, -1 = +2
Which means that all of these arrays are acceptable, at least by the sum-of-modifiers rule; however, the +2 arrays are indeed non-trivial to work with.
However, character class and construction has much more to do with this than ability scores alone.
Character classes and builds in D&D generally depend on one or more attributes to do their job:
- For a Fighter, this is either Strength or Dexterity, but Constitution also helps
- Rogues are all about Dexterity, and can make use of Intelligence and/or Charisma
- Clerics and Druids rely highly on Wisdom as it is their casting stat, but also benefit from Strength and to a lesser degree Constitution.
- Wizards are all about Intelligence, but are helped a bit by Dexterity as well
- Sorcerers rely on Charisma and also receive a little help from Dexterity
However, not all classes are this simple, or Single Attribute Dependent (SAD). Some classes, unfortunately, are Multiple Attribute Dependent (MAD), which means they have features and functions that key off of different attributes:
- Rangers rely on Wisdom for their casting, but need Dexterity heavily for combat and benefit from Constitution and/or Strength.
- Paladins are equally troublesome, as they need Strength (or possibly Dexterity) for their melee combat while using Charisma for their casting and paladin abilities. (PF actually fixed the worst of this -- the 3.0/3.5 Paladin used Wisdom for casting, which was terribad as it meant the character had to have 3 good attribute scores at a minimum.)
Furthermore, some character classes can afford to "dump", or take a penalty in, certain stats:
- Fighters can generally dump Charisma, as they aren't expected to negotiate their way out of situations
- Wizards often dump Strength, as they aren't getting into frontline combat
- Clerics and druids will frequently dump Dexterity, especially if they aren't using ranged weapons or have Zen Archery -- that feat also allows for SAD archer Rangers, relying entirely on Wisdom.
Overall, this means that P1 and especially P5 must be more careful with how they build their characters. P5 is going to have to go with a fully SAD class with an easy dump stat, for instance -- if they're dead-set on a Paladin or two-weapon fighting (aka dual wielding) Ranger, I'd let them reroll because it's not compatible with their stats array. However, that array would make a reasonable Fighter, Cleric, or Druid.
P1 is a bit more interesting, because they have a double dump on their hands -- most classes only have one designated "dump stat". It is still possible to be effective with two stats dumped, even as severely as that array dumps them, but it takes care to avoid backing yourself into an unexpected corner by dumping the wrong stat. (Dumping Intelligence, Constitution, or even Charisma can have unexpected side effects in certain games -- it may be the case that characters with a low Intelligence will not be able to speak properly, low-hit-point/squishy characters will have trouble surviving first level, or a particularly uncharismatic character will be run out of town before the adventure can get off the ground.)
Footnote: these lists are incomplete -- I don't have experience with all the 3.x or Pathfinder core classes
Bonus: Racial bonuses shouldn't be used to "fill holes"
As to P1's racial attribute bonus? It should go to the dependent attribute for P1's build, not to fill a "hole" in their attribute scores -- you're basically always better off putting it in the strong suit, especially with a +2 bonus because that translates into an unconditional +1 to the derived modifier.
Best Answer
Explain the problem to your players
You can certainly ask a player if they would be willing to redesign their character. If you explain that there is a missing skill-set from the party thy might even prefer to change their character because it can be fun to fulfill a unique party roll.
If you prefer not to have them re-make their character there are several other ways you can try to make the game playable in a style you are comfortable with:
Allow alternative skills for intimidation/persuasion
You can communicate to the players that you are open to using alternative stats for skill checks in appropriate situations. If they want information out of someone you could make clear that you might be willing to allow a STR + Intimidation check if they try to intimidate through a feat of strength.
Provide other ways to investigate
Another option would be to allow for clue gathering from Wisdom (Insight/Perception), and Dexterity (Slight of Hand to lift clues from someone's purse). You can try to arrange for opportunities for their strengths in other Stats to partially compensate for weakness in Charisma. For example you can try to arrange for more charismatic NPCs to be willing to assist the party in exchange for certain services rather than by being persuaded or tricked.
Communicate game-style norms and expectations
Lastly it will likely be important to communicate with your players what you expect the style of the game to be like. They can have a bunch unintelligent, uncharismatic characters but they can also choose to interpret how those weaknesses are expressed. Being uncharismatic does not equal being wildly violent. If a character tries to use force inappropriately to solve a problem you can enforce consequences. Alternatively if they find a way to succeed despite their weakness you can reward them. The challenge of finding ways to work around their characters' weaknesses can make the game enjoyable just as much as the satisfaction of playing to their strengths.