After patch 5 hit (but before hotfix 12), I started a new game and made a Wizard character. She and Shadowheart handily defeated the 3 intellect devourers on the Ravaged Beach without much trouble. However, I remade the Wizard after hotfix 12 (I'm kind of dumb that way), and now the beach brains are kicking my sorry aft-section all the way back to noob-hood. What changed?
At first I thought it was the brains spamming Dash, but after re-reading the patch notes, it looks like that was implemented in patch 5. That said, I don't recall seeing dash-spam before hotfix 12.
I've made three post-hotfix 12 attempts so far with the same character. First time I went in with my old strategy - 1) blast the nautiloid tank (but I replaced Firebolt with Chilling Touch, and it turns out Frost Bolt doesn't set things on fire - who knew?), and 2) kite the brains while spamming cantrips. That's when I discovered the terrifying power of the new NPC Dash feature. TPK.
Second time: 1) Buff up with Divine Shield and Mage Armor and 2) aggro the closest brain in the hopes that we could kite it to death before the others woke up. Again Dash, again TPK.
Third time: 1) Hit the nautiloid tank with actual FIRE (it worked; one brain down), 2) buff up with AC spells, 3) kite and cast ALL the spells for as long as I could. This time the party went down faster than NSFW things that go down really fast, but I did manage to kill two of them before Shadowheart got one-shot by a 2-HP brain.
One thing I haven't tried is using any of the consumables you get on the Nautiloid (besides healing potions). Might try again next weekend, but in the meantime, any tips would be welcome.