The Weapon's Refrain (Ultimate) synced weapons bug

[Hussain]

The same happens if you go second coil savage as a character with lvl60 or 70 weapons. The dreadwyrm weapons i135 are better than a synced down i405 weapon. It actually makes a little sense there because you shouldnt be allowed to get better gear than i130 because it was the max ilvl at lvl 50. But in ultimate i345 and i375 are allowed.
As you said the current sync system doesn't take 5 ilvl difference into account for weapons. Any weapon higher than i370 (when not diamond i375 weapons) will get synced down to i370.
I am unsure why you think it is only physical jobs that are affected, mage/healer weapons are -1 weapon damage too at i370.

Also another thing to point out is what you said here "because you shouldnt be allowed to get better gear than i130 because it was the max ilvl at lvl 50" this isn't true in ultimates because you can get better gear than savage by getting dung gear and the same thing applies to relics.
So the fact that relics only in The Weapon's Refrain (Ultimate) synced down to 375 with the same stats as Diamond weapons but the weapon dmg for physical jobs is 100% a bug cause it doesn't apply to casters.
go test it if you want
I'm sure SE are aware of it