Dungeons and Dragons

Everyone has bad dice days. Everyone has that one time you get a Nat 1 at a critical moment.

But guys, my party is in trouble.

They're consistently rolling terribly in combat across multiple sessions, classes, and dice types. And I mean terribly. Over time, you'd think their d20 rolls would average out to about unmodified 10, right? Plus or minus a bit. Hah. No. They're averaging about 7. Other rolls (damage, healing, etc) also often suffer from this. It's turning combat into a slog; anything with an AC of above 12-14 or so is proving awful to fight, and when attacks do hit they often do little damage.

We're all experienced players, and it's a digital platform - so I can both know they're not missing modifications to the raw d20 roll, and know it's not "bad dice". Unfortunately, they're also experienced enough to figure out ACs from misses/hits, so it's not like I can even give them "free passes" on attacks as anti-frustration measures.

It's at the point where I'm thinking the honest only way to "fix" this is to artificially nerf NPCs or vastly reduce the CR I'm used to them being able to handle. Is that really it, folks?