P.s. Shouldn't we give orders to the troops? It seems the most important thing to me actually. The enemies have the dark blessing of their respective divinities, we can use that knowledge.
You can give them specific orders or leave the details to Fanriel and Urskoy.
I don't think magic is a limited resource there, this isn't Total War Warhammer.
It is and it isn't.
It
is possible to temporarily exhaust the available magic in a given area if there's a lot of high-power spells being cast in quick succession, but barring something specifically preventing it, the Winds will be constantly bringing in more magic as it flows in from the Polar Gates, replenishing the magic available to use.
Running out of magic isn't really a relevant concern at the moment, considering Fanriel specifically lacks high-power spells, can tap into any of the eight winds if one runs dry, the relatively small amount of wizards present on the battlefield, and your proximity to the Polar Rifts. A more relevant concern would be mental exhaustion, but Fanriel has been relatively restrained with her spellcasting so far, having cast two Lenses in the Sky, two Cerulean Shields and one Arcane Bolt, spaced out across the entire length of the raid so far. You'll notice when Fanriel starts to feel tired.
summon as many Lesser Ghur Elementals as you can
For this, I would need some sort of clarification on what you mean by "as many as you can".
Because by literal interpretation, it would be "Fanriel keeps casting until she is physically stopped from casting, miscasts, or drops unconscious from exhaustion, whichever comes first". And I want to confirm that that's your intention before going through with it.
Also, if you're summoning Elementals, you should specify what orders you are giving them, keeping in mind that these orders cannot be changed once the Elemental is on the battlefield. You could order them to "Attack the Livgard", in which case they will go on the offensive as soon as they are created, or "Protect [Person/Group]", in which case they will follow them and engage whoever they engage. But especially if you are splitting your forces between the Livgard and the Shamans you need to specify where the Elementals are going.