I think the growth hacking/engineering role/persona is especially now building up as a core skillset as product decisions need to be made way faster and way often than ever before (thanks to realtime usage data and very short release cycles).
This basically puts way more pressure on making the right decisions for the product & its marketing (in a holistic cross-functional way). A thing that traditionally was handled 'well enough' with several people/departments that communicate.
In a nutshell it is a product management position but with emphasis on marketing and growth. Depending on the lifecycle of your company this is the job of the founders/CEO or the product manager or a dedicated CMO. All in all the skillset in itself is very very valuable and there is not enough good material on product management and cross-functional agile marketing.
I am contributing content in this area and hope more and more people will follow. There is a ton out there that solely focuses on marketing (low barrier to entry) but not much quality content on the intersection of marketing & engineering & ux.
If you are interested in growth hacking feel free to check out my upcoming book:
https://www.blossom.io/growth-engineering
Also very happy to help anyone who'd like to grab a coffee/tea with me in San Francisco or Bay Area or via email, twitter, hangout. Feel free to get in touch.