Charlaquin
Goblin Queen (She/Her/Hers)
This is just a feature of the Class design though. Getting Fighter AC on a Barbarian is possible even with Array or Point Buy stats, it just takes longer to get there. And comes at the opportunity cost of using all your ASIs on Con and Dex instead of Feats and/or other abilities. But still, Barbarians being able to compete with Fighters in the AC department while lightly armored is a feature, not a bug, and if the Fighter has equally high Ability Scores, he’ll outshine the Barbarian in other ways, such as having way more Feats.It doesn't necessarily break the game, but it can skew the balance in a way that requires the DM to adjust other factors to compensate. For instance, in the above example, a level 8 Barbarian in a loin cloth has equal AC to a level 8 Fighter with Defensive fighting style, due to a combination of unusually high Dex and unusually high Con, without any sacrifice to Strength. The Fighter gave something up to get that armor class, and having an AC that high is meant to be reserved for the folks in heavy armor, to compensate for the drawbacks to heavy armor.
By contrast, I had a level 8 Barbarian made with a point buy. I don't have the sheet in front of me, but her AC was either 15 or 16. I know I put at least one ASI into Con. Comparable to a Dex character at that level with light armor.
If everyone has super high ability scores, the classes should be just as balanced against each other as they are when everyone has average ability scores. The ability scores seem in the OP’s game just set a higher baseline for everyone, there’s something else going on that’s allowing the other players to break the bounds of that baseline. Most likely magic items and/or rules being interpreted strangely.