Yes. Legion / Snow Shields work excellent for this battle. According to a video I saw, Conviction and Stun Blocks seem to help greatly with this battle.
Here's what a good team for this battle is.
Life- For Healing Ice- For Damage and Dispels Storm- For damage Balance- For Blades
Also, there are certain things that trigger Young Morganthe's cheats. _________________________________________________________
0-pip Mammoth- RANDOM (Not exactly known)
Earthquake Nova- Using damage or healing spells that provide an extra Charm or Ward (Rebirth, Storm Beetle, Snowball Strike) will trigger a normal earthquake on everyone, only to backfire on her doing 100 Fire Damage to herself. This is followed by a Power Nova dealing 700 Base Damage on everyone, also putting the usual -25% charm on team.
0-pip Mana Burn- Anyone that goes over 8 pips will be hit with a 0-pip Mana Burn spell. Strangely, even though she uses up no pips for this spell, her damage is equivalent to the amount of pips she currently has, (including power pips)
You may want to refrain from using Rebirth, as it gives absorb armor, triggering the Earthquake Nova cheat. Instead You can try to use Unicorns or Life Bats. Satyrs heal a huge amount, but only to 1 person. It could work if some people use it consistently, but I reccomend not doing it, as it wastes pips.
Also, Try not to get TOO caught up In healing your friends from Mammoths. Throw in as many attack spells as possible. Don't bother using too much blades, just go for it. If pulled off successfully, you should have the perfect ratio of healing and damage.