Spoilers ahead.
First one off the top of my head that stands out is the
spoiler
House of Azath taking out the Jaghut tyrant in Gardens of the Moon. All this buildup to the tyrant's awakening, he rampages through the countryside on his way to Darujhistan, mixes it up with Tool and Rake, but ultimately it's a magic tree house that got no real build-up or proper lore treatment in advance that takes him out.
Fits beautifully with all his lore, but the timing and use of it in this particular book felt like a deus ex machina to me.
You are not alone. I've had the same experience and I'm wondering what the big deal is. The books are really good, obviously, and a master class in world-building, but I find a lot of the deus ex plot elements disappointing.
I'm only on Memories of Ice, though, so what do I know?