I just lvl my barb from 65-70 in may be 1.5 hours? (casual playing)

Just focus on those super high reward bounties (which will be nerfed big time when patch 2.1 come)

Act I - Clear Khazra Den
Act II - Complete event: A Miner's Gold
Act III - Clear Cryder's Outpost (2nd best, easy to find and easy to clear)
Act III - Clear Forward Barracks
Act IV - Clear Hell Rift level 2 (best, because no need to find the location)
Act V - Complete event: The Miser

Each of them will reward you 9-12 mil of exp upon completion.