My question is:
System suggests to pick Light's Decree - Spell - World of Warcraft in Azerite Traits for holy paladin m+ default setup on shoulders. The question is why
As many traits do, Light’s Decree has two independed parts:
It does some damage when spending Holy Power during Avenging Wrath/Crusade.
It increases the duration of Avenging Wrath by 5 seconds.
While the first part obviously only works for Retribution as the other specs don’t use Holy Power, the second part does indeed work for all specs. Increasing Avenging Wrath’s uptime is often worth it and using it on one item can be extremely strong especially when combined with the Sanctified Wrath talent and the Glimmer of Light trait.