When I started playing on Warmane the polearm "Oathbinder, Charge of the Ranger-General" (HEROIC) was available to purchase with points, and now that I've reached 80 it is no longer available, I can only find the normal one.
Am I not seeing it or has it been removed? if removed, what's the reason behind this change?
No, never has been available for points ;) Only normal version. You probably looked in the shop at the coins section by accident before.
Heroic items like this never made it there.