I've been experimenting extensively, and I've my Pi-Hole to reliably block Hulu ads without causing errors on desktop, mobile, and Chromecast.
The key seems to be setting things up so that SOMETHING I served to the Hulu app, but not blocking the domains that the app then reports back to.
I'll post the lighttpd.conf and pihole-FTL conf files as soon as I get back to my laptop.
Tl;dr follow the guide below, but don't block or redirect vortex.hulu.com or doppler.hulu.com
https://jacobsalmela.com/2014/11/19/attempting-block-hulu-plus-video-ads-raspberry-pi/