I have lived in Abbotabad for seven years and i have to say the Hindko belt is more developed and wealthy than majority of the districts of KPK. Kohistan is backward due to its remoteness. You have not been to southern districts of KPK, very poor and backward.
Peshawar valley is very densely populated, 9 million people, and very fertile lands, their politicians also ignore southern districts of KPK, as they do not get vote from there.
If you ask me, Hazara (east of Indus) was a distinct administrative unit under Mughals and attock was part of it. Sikhs also administered it separately from Peshawar. You people have justified demand for new province. But do demand Murree and attock from Punjab. Then you will see how much Nawaz shareef and PML_Q were/are sincere to cause of hazara province.
Attock wasn't a part of "Hazara Qarlugh" under the mughal administration. It was governed by the Gakhars, who according to Ain-e-Akbari defeated the local Awan, Jodhra and Khattar tribes. The hindko speaking of Attock is only the Chach illaqa around Hazro city. The Pindigheb, Fatehjhang, Wah, Attock city areas are all Potohari speaking and ethno-culturally Potohari. The people of Murree are "Pahari", which is quite different to hindko. Pahari and Pindiwali Potohari are more or less the same languages with a different accent.