Perhaps everybody's favorite event, and yes, it’s very powerful. Extra attacks are always great, extra from the same unit, are even more so. It’s negative - losing the unit, can be a bonus for the Fungal Dwarves which like to see their own units dying, even more so if it’s to make a Spore Carrier die before the end of turn to become a Fungal Beast.
Remember you don’t need to choose a unit that already attacked, so it can allow you to attack with 4 different units.