Astral flow burn for TotM stavesFollow

It'd be possible to, but probably not advisable, since I believe that, like Black Magic AoEs, Astral Flow bloodpacts receive a damage cut when hitting multiple mobs. One of the reasons that burning mobs down with Charged Whisker for Blue Mage is that it doesn't have that damage cut, regardless of how many mobs you hit. If you hit one mob for ~7000 with Charged Whisker, then, barring resists, 10 mobs of the same level and type would be hit for ~7000 as well.

That being said, if they can be burned down that way, your Atma choice would depend on what avatar you're using.

The two below would be pretty much universal to what avatar you used.

Atma of the Ultimate
Atma of Hell's Guardian

Then for the avatar specific ones, I'll list them separately

Carbuncle - Atma of the Beyond
Fenrir - Atma of the Cosmos
Shiva - Atma of the Beyond
Ramuh - Atma of the Lion or Atma of the Blinding Horn (either one would work)
Ifrit - Atma of the Lone Wolf or Atma of the Smoldering Sky (either one would work)
Garuda - Atma of Gales
Titan - There isn't an Earth element Boost, so something like Beyond would work fine
Leviathan - Same with Titan. Would again recommend Beyond.

You're probably better off using Shock Squall + Thunderspark + Cataclysm in a FC/CW group. SMN makes for very good AOE crowd control.