Have you guys ever been in this situation? You roll up a character with a fairly standard archetype -- big dumb guy with greatsword; snarky necromancer; etc. -- only to find that another player is horning in on the same conceptual space. Is this a "stop copying me" problem, or do you feel like there's enough room in the campaign for similar character types? And if the players in questions do feel like, "I called shotgun on seductive bard," how did you resolve it?
I would probably focus on what sort of hole in the party a character very similar to yours might leavee. On its own, for example, a second big dumb guy with a greatsword in a large party probably isn't a problem -- and I am right now reading a novel about an adventuring party with two necromancers in it. But if the party is small or otherwise doesn't have all of its bases covered, that duplicate character may prove to be not very helpful.
One issue that may come up is that a player is replacing a PC who died, and he has no idea what he could do slightly differently to keep that sort of character alive -- so he creates a radically different character who leaves a big hole in whatever area he was covering before.
Still, I would generally prefer to find some way to distinguish my PC from others in the party who superficially seem to be filling similar roles.
How are you playing and for what purpose? If you have a group that is playing in living campaigns using standard modules that cannot be varied then I can see that you need a standard balanced party that can cope with a full range of standard encounters. If you are playing at home for fun with a single DM (or even your own several DMs) then the adventures can be modified to allow for the characters that the players want to play and the style of adventure they enjoy.
All fighters with no healing or magic? Fine, adjust the parameters accordingly. Remember that it is possible to do subdual damage, don't include any magic-using opponents or allies, allow time for natural healing, talk to people you meet rather than shooting first, use cover (that surprised my DM when I did it!), run away (I got XP for that!).
Finally, imitation is the sincerest form of flattery. If someone is copying your character concept you have clearly played it well and made it look fun.
I really enjoy having wonky parties. The lack of a certain role being filled just adds an interesting challenge and encourages you to think outside the box when facing encounters. Your party has three tanks and no healer? Have your tanks rotate who is in melee with the big monster to spread the damage over three big hp pools.
Your party is three rogues and two rangers? Approach every encounter in stealth, do a big alpha strike on the most dangerous enemies, then fade into the night and ambush the enemy as they try to pursue you and stumble into the pre-prepared ambush zone your rangers filled with traps and your rogues filled with caltrops.
Weird party compositions can be really fun if you approach things with the right attitude, and there are usually magic items or class options to fill gaps if you desperately need to have a certain role covered.
Weird party compositions can be really fun if you approach things with the right attitude.
That's the thing... I'm not worried about this for myself, but for my players. When it's somebody else who feels crowded out of their own niche, I want to have the pep talk in my back pocket to help 'em have fun anyway.
I'd seek to resolve this by tweaking the stats on either, if they're too similar. Skills can usually be different. I've played with great DMs who join the character creation, hinting at what skills I might want to take, because she knows the members' stats. Skills are the go-to place for tweaks, since they matter a lot in exploration and downtime.
I've always had more character concepts than I've had groups to play with, so never actually encountered this problem myself as I've been happy to flex. I've also played pretty fun party dynamics with "twin" or "clan" concepts, so there might have been a sorcerer and her two bouncers like Tweedledee and Tweedledum.
Don't get me started on people copying my character.
Most of the home groups I've played with tend to be pretty open about wanting PCs to be distinct from each other, because it means everyone gets to be good at something different. It also makes it easier for the group to cover all the essential roles. However, niche protection discussions still come up every so often, and sometimes mid-campaign. For example, in one campaign, when the party reached 7th, one player took Leadership, and it took us a while to settle on a class for the cohort that didn't step on anyone else's toes.
Duplication is much harder to avoid in organized play, where the party composition can be pretty random. Warhorn can help mitigate that, but only if everyone uses it. I've seen a number of players (including myself) call an audible at game time to switch to another character who better covered a missing role or who will overlapped less with another PC. But sometimes you may not have much choice in who you play in a given tier, especially if you're newer to the campaign. And sometimes a more veteran player has lots of options but *really* wants to play the latest installment in an ongoing storyline with the same PC they used in all the previous ones.
I have seen a certain amount of deliberate copying of character concepts in our local community. Sometimes it's simply because you see another player's character in action, and want to try out a race, class, archetype, or combo for yourself. (I'm guilty of that, with my heavens shaman...who has ironically reached Seeker before the PC who made me decide to try one.) In a couple cases, it's been a out of a perverse urge to "do it the 'right' way" after seeing another player's take. (My daughter made a bones oracle who was delightfully spoopy, unlike a certain problem player's obnoxious one. And one friend built a frighteningly effective archer partly in reaction to a novice player completely borking his own up.)
That's the joke. /McBain