I was expecting a rage thread to be honest. Grotesques can be a really bad monster to encounter as massive crowds when you have really tight corridors in the tile set layout.
Their explosions are ruthless at high GR tiers and have a small randomized explosion timer once they’re dead just like Molten elites. You need to ensure you take the aggro of the lot of them before you wipe them out and evacuate the area of effect quickly.
Although, I think the reason that they present in an Orek’s Dream is the eels’ impact on the combat. After the explosion, the eels they left behind is the best monster you can encounter to use as a beacon for your area damage against a large group. They’re easy to lure, have above mediocre movespeed and has a small frame to stack them in between other monsters.