I remember I was the one doing the LBing, immediately after the Malkuth knockback you can LB, hit both the storm and Seph and get away before the yellow flash comes. Using the melee one seems like a waste, since the MCH LB nearly one-shots the storm and gives you some damage on Seph to boot - melee one is going to be overkill.

Caster LB is a thing as well if your healers are up to the task. With the right positioning, it can hit everything including Seph but you're going to get a huge spike of explosion damage from the small adds dying at the same time.