D&D 5E Some guys want to run a campaign using a Sorcerer, Land Druid, Wizard, and Lore Bard only.

[Waterbizkit]

The biggest issue I see is that all of those classes have a low AC. This, coupled with the low range on most spells, means that they are very vulnerable to being picked apart by ranged fire from even something as simple as a group of CR 1/4 goblins using hit-and-run tactics. If they ever run into a group of drow they are likely to suffer casualties or even TPK.

Whether or not that will be an issue depends on whether goblins and drow (and centaurs, etc.) exist in your campaign in sufficient numbers for the inconvenience to make itself felt, and also on whether the PCs are prepared to use other techniques such as Invisibility + Pass Without Trace to deal with such threats in an alternative fashion.

It could work, or it could fail horribly.

Fog Cloud. A 1st level spell that three of the four party members have access to. It's not a win condition against ranged attacks but it certainly helps and it's available right out of the gate. Two of the party members get darkness as a 2nd level spell as well. Things only get better from there and once the party hits 5th level the druid now has windwall which makes all ranged weapon attacks, short of a giants boulder, miss automatically while the party can sling spells without issue.

The more I think about it the more this party is a nightmare in an enclosed space as long as they pick their positioning correctly. Web, spike growth, grease, gust of wind, stinking cloud, slow, sleet storm, hypnotic pattern, it goes on. These are all spells of 3rd level or lower and obviously don't even account for other utility spells that a party of four full casters can stack. The only limits are their imaginations and their spell slots...

Either way, I'd hate to be the goblin archer who has to slog through the fog cloud over terrain that's been greased, webbed and spiked for good measure.

 

[Charles Rampant]

It feels like the biggest problem here is not their ability to win combats, but their inability to step on each other's toes, in terms of roleplaying / character niche. I had something similar in a one-shot I played in; everyone else was some kind of caster, including two fighter/wizard multiclass attempts, and my Half Orc Champion Fighter ended up being the more distinctive one there.

At least, I thought so...

 

[FormerlyHemlock]

Fog Cloud. A 1st level spell that three of the four party members have access to. It's not a win condition against ranged attacks but it certainly helps and it's available right out of the gate. Two of the party members get darkness as a 2nd level spell as well. Things only get better from there and once the party hits 5th level the druid now has windwall which makes all ranged weapon attacks, short of a giants boulder, miss automatically while the party can sling spells without issue.

The more I think about it the more this party is a nightmare in an enclosed space as long as they pick their positioning correctly. Web, spike growth, grease, gust of wind, stinking cloud, slow, sleet storm, hypnotic pattern, it goes on. These are all spells of 3rd level or lower and obviously don't even account for other utility spells that a party of four full casters can stack. The only limits are their imaginations and their spell slots...

Either way, I'd hate to be the goblin archer who has to slog through the fog cloud over terrain that's been greased, webbed and spiked for good measure.

Why does the goblin archer need to slog anywhere, even if there is a Wind Wall? He's got Stealth +6 and bonus action hide. Why can't he just wait until it goes away? He can sneak off and come back in five or forty-five minutes.

I'm not saying Fog Cloud/Wind Wall aren't good ideas (although a lot of DMs like to make Fog Cloud block line of sight in both directions, which makes it actually hurt the PCs). I'm not saying the party is doomed. I just think that low AC is the biggest gap I see in this party's armor, and the thing I would spend the most effort on mitigating if I were one of them. E.g. switch the wizard out for a Fighter 1/Wizard X.

 

[CTurbo]

I am very much behind the idea of them running with a whole party of full casters. I think it'll be interesting. They're certainly going to excel in all out of combat situations. I'm just worried about their low AC and lack of HP. It was going to be a Sorcerer, Wizard, Bard, and Warlock, but I recommended there be at least 1 high Wis character. I'm not sure which school of wizardry he wants to take. Pretty sure the Sorcerer will be Wild Magic.

I have played in a 5 player party of Fighters and it was really fun and successful. We had a TWF, a GWM, a S&B, an EK, and of course an Archer. The DM had to toughen up the combat encounters because we would roll over standard CR enemies. That is why I'm thinking I'll have to scale the combat toughness back a little with the squishy party. Yeah they'll have a lot of control but they're not going to be able to keep enemies off of them all the time. or so I'm thinking....

 

[Aldarc]

No, no, no, no, NO!! (Channeling Billy Crystal's wife in the Princess Bride)

Let them play what they chose. Don't alter the party composition because you think they need something else. Don't alter the adventure (much) to adjust for party composition. Just try to make it as fun, "real" and adaptable as you can. Let creativity flow!

No, no, no, no, NO!! You are missing my point entirely. It's not about altering party composition because I think they need anything else. It was about being the jerk of a DM who gives them a crutch only to jerk it away at the point they reach tough terrain. It was more about supplying a campaign hook than anything else.

 

[TerraDave]

It has the potential to be quite a strong group. I would be more worried about challenging them then squishing them, especially as they get to mid-levels.

They will want to summon things.