xenon total dmg vs attack

Weapon multipliers apply to stats too and are just a multiplier to everything, not just attack. It does not cause attack to be worth more, as far as I'm aware.

Weapon multipliers make +ATT worth more. So, for example, a +100 attack Onyx Apple increased an NL's range more than it increased a Shadower's. Once, before potential and the power creep hadriel mentioned, it was something to consider. Where it comes to %ATT, though, the multiplier is, as you said, irrelevant.