Night of the Gray Death Final Boss(Spoilers!)

This post contains major spoilers for Night of the Gray Death!

My players are about jump into ch3 and I have some concerns about the final fight with the Conquerer Worm, mostly that I've read it can be a bit of a pushover for lvl 19 characters. Does anyone have any experience with this fight? If the fight is too easy, would it be a more exciting/challenging with extra spell buffs or minions?