Ah yeah that sounds about right, It could do with a complete tuning pass to potentially make the materials a little more abundent on the middle and lower difficulties.
By starting early you were at least able to get through all the upgrades, which is great. I'm not sure how long a playthough on the hardest difficulty would be for someone playing for the first time - but it could easily be 2.5 - 3 hours I think (far too long I know). But then crafting probably gets better, at the expense of the rest of the game.