My suggestion is to return the skill points back to Harbinger.
A secondary suggestion is to grant them Spellcraft as it makes no sense from an IC perspective, they are a spell casting class, yet do not have the skill to understand how they cast spells without multi classing.
I would also request that the syngeries it has (via feats) works as a Shaman does. A shaman gains the benefits of the feats in Barbarian/Ranger/Monk by taking levels without taking feats. If this same mechanic could be brought to Harbinger it would expand on the multi classing built into the class while keeping the majority of the levels as Harbingers providing unique build diversity.
Final suggestions is do not force Hexblades to become Harbingers. With some of the post release changes I am happy for my Hexblade to remain a Hexblade. I do not want him to lose his familiar. It was nice for his RP.