Astro lumonious aether was 15 seconds when it first came on a 2 min cd just like shroud of saints but in 3.2 it got increased to 24 seconds and in 3.4 with the buff to celestial opposition, they had a strong mp economy back then as well.
And has the option to extend to 34s with CO.

I think that our mana household should also be our job. Even though I was really sloppy with LD at the beginning of the add-on. I also think it's good that every healer has a common component in the form of LD and also keeps his mana household with job-specific skills.