It's a numbers game.
Small-scalers build to be tanky enough to survive multiple people beating on them, but to have enough damage to burst someone down when they all coordinate it.
Everyone else therefore builds to be able to survive this coordinated burst (unless caught with their pants down), and have enough damage to contribute to zerging someone down.
The extra siege damage hasn't helped either as people are also building to survive that.
Hardly anyone builds (or can build) enough damage to take down a player alone anymore. The trade-off just isn't worth it..
I've no idea what the answer is.