[quote=@Silverlight138]
Just to have a go at it: 

Cherubims to heal people when the earth gets fucked over.
Guardian angels for divine transportation out of the eventual hell-hole.
Seraphim angels to assist in the physical devastation of the earth.

-sigh- I feel like I'm in school. Yknow, those kind of questions which you think you perhaps know the answer to, but end up getting them wrong.
[/quote]

No, you're exactly right!!! You get a cookie

Edit--
Well, almost exactly right, just slightly different. 
Cherubims to ease their suffering as they perish so that they would go painlessly (takes many cherubims to do on such a large scale, same for the others)
Guardians to, yes, escort the souls to where they need to be.
And Seraphims to indeed, be the ones that destroy the actual earth. 

All of them had a very important role to play in the destruction of earth, which is why all three were necessary.