I just soloed the entire Phase Spider lair with Gale without ever being attacked.
Spell > hide every turn. Spiders go "Skitter!" and do nothing because you're not in a vision cone. Flashy spells like Shatter or Magic Missile don't make them at all interested in trying to find me.
Kind of ruins the entire game when you think about it. It has been like this for 2 years so maybe they like their mechanics and clever stealth play.