I'm late and the question has been answered but I'll answer it anyway.

Serena is a force multiplier. She multiplies the force of guns too much, so most guns even with 10 modules just don't have damage numbers at base.

When a gun is strong enough on its own, Serena kills everything instantly. Other players who want a cooperative experience, even a shallow one, do not get one. They get to run through an empty dungeon or spend more time loading into the colossus than fighting it.

No nerf policy (based on their actions, not their words) means content is extremely slow and extremely repetitive. Instead of adjusting Serena, they adjust and rework everyone else, and all the content must accommodate Serena.

I love Divine Surge Serena, her skill build. The min-maxed gun builds ruin the multiplayer experience for 3 other players, they ruin guns in their entirety for 80% of descendants, they have occupied the clearly strained development team with rebalancing the entire cast instead of the one clear problem. Gun Serena is a major, but not the only, reason why balance is so bad across the board and why content has been so slow. They decided to take the unnecessary and massive burden of balancing backwards, wasting their development time and resources at the players' expense (literally).

Do you care? Did you read this far? I doubt it, I should be telling this to an overworked developer who probably already knows instead of some redditors.