[Spoiler] Red Wizard's Gambit

No idea where to post this, so if this is in the wrong place, feel free to direct me elsewhere - 

The first encounter from the season epic as far as CR is great, right at deadly for the expect five level 3 characters. A perfect place to start an epic!

But...

The primary threat has 3 abilities, all of which are explicitly negated by the scene, and one disadvantage, explicitly enforced by the scene. The result is a rather small pile of hit points that is expected to do near - 0 damage in the encounter. I know the Red Wizards aren't the brightest of villains, but... come on. "Let me summon this terrifying creature, then leave and let it bake to a crisp while the PCs put it out of its misery" isn't even a bad strategy, because it's not a strategy at all. There's even a tactics block to help the DMs run the encounter, which covers a really cool mechanic for other things going on, but no mention of what should be done with this limp noodle of a centerpiece. :(