After the king asks him to serve as his advisor, the lord of the North discovers the murder plot of his predecessor as an attempt to cover up the heir’s illegitimate claim to the throne.

Sounds like an interesting logline. I would be interested in reading more.

I think this is the best plot for the logline.

However, when the series was described to me from friends in 2013, the white walker plot was placed right upfront, as well as the fact that the seasons last about 10 years. I was hooked, but had to ask, 'wait, there's kings and queen's and stuff though, it's not just villagers running from monsters right?' I received a 'yes' and was really drawn to the fact that the kings and queens didn't know about the white walkers.

True, the books had already provided a "built in audience", so the pitch would have been a mere technicality at best.
I was just trying to logline a complex narrative.