[Fern]

A good bunch of the Hexer spells are not compatible with Rotwood, actually, since it only works with Huggessoan domain spells. I'm not saying it's entirely useless for Hexer, but taking a peek at the amount of Huggessoan domain spells that'd work with Rotwood would quickly show that it isn't all that useful to Hexer compared to a tome, since the biggest ones (Wretched Oil and Black Bubble) are Isesip and Aquarian, and the utility invokes in general don't need a casting tool.

The one thing that benefits from Rotwood the most is Void Assasin and even then if you're going void mage it's usually better to run a tome for +5 Skill Slots since VA is pretty hungry for slots.