I used to do queen (normal), warriors rest (normal), zolton (normal 14-50), queen (hell 50-60)... Took at least 40 hours, this was when I first began using DB.
But now... I use my other toon to get 1-12 in like 1 hour max, just keep killing zolton on normal... Then jump over to warriors rest and afk for 1-2 hours, come back, give him a good life on hit weapon and run him on bastions keep on normal, nightmare 40-50 and hell 50-60. I can get 60 in about 24 hours. Probably less if your monitoring it... Since it'll be slightly faster if your manually avoiding getting stuck in various circumstances. Shouldn't get stuck if your using a ranged character though. My melee barbarian gets stuck cause... He doesn't go around this stupid catapult LOL