IIRC not every Valdun bonus was 2h exclusive, but the Crate nerfed it very early in AoM (like the first hotfix after release) cause some melee stuff were too strong with it.
The pierce values were way too high on the items and set bonus, hence why it was nerfed. I believe Valdun’s passives have been always 2H ranged exclusive, so melee didn’t benefited from them.
Secondary problem for physical ranged cadence specifically is that all the multi-shot and shotgun WPS are straight up worse than normal weapon attacks thanks to how they interact with armor. That not only gimps your AoE compared to other damage types, but also slows down charge generation.