If a target is directly hit, they will suffer 2D6 bludgeoning damage, followed by 6D6 fire damage. With each additional fireball strike, the fire damage increases by 2D6 damage dice, so the second fireball does 8D6, the third does 10D6, and the fourth does 12D6.
Basically, before the third fireball hits, anyone below Transcendent, including those Barbarians and warriors, will likely be down. When the fourth hits, most Legendary frail professionals will also fall.
Currently, Dilila is not using the high-intensity damage of this spell, but instead its controllable explosiveness and powerful flame impact to neutralize the dense moisture of the Revenge Storm, restoring visibility here.