Hell mode, Act1 Trailing the coven.
Complete quest checkpoints up through the bridge until you get the "Explore Leoric's Mannor" check point.
This area has many shrines, and usually an XP shrine, and elites @ the beginning.
Once you clear outside, go in and a swarm of easily killable mobs will pool @ bottom of the stairs.
There might also be a Purple guy in this area.
W/ XP shrine was getting ~125K for a ~45sec clear. Never less than 40K xp / run.
pick up gold/ items, tp to town, exit game.
Resume game starts you right back at the top of the courtyard outside.
Rinse Repeat.
Took a minute to get the the right spot initially, but after it was set up, was , for me by FAR, the best spot to grind.
Decent gold too.