Normal Crusade will dish around 4-6 mil more damage over the course of 30 seconds which I timed on my clock.
Radiant glory cannot do that but I am thinking that you have a go every 30 seconds instead of 2 min cd on Crusade.
Yes, you can pump way more with Crusade on but if they pop walls, you are out for 2 mins when Radiant Glory can go again soon.
From what I have seen dawnlight does not stack.
So this means that radiant glory on herald is actually bad, because if you Wake you can get 2 of them, and if you get crusade/AW on, you get 4 automatically, so if you run Radiant Glory, you get 4 and waste the 2. You still get them with your next 2 spenders, but they don’t stack so it just reset.
I could be totally wrong and dawnlight stacks. No idea.