Hey Guys! Malthael campaign T6 is currently bugged and gives 243 million exp! Will be fixed REALLY soon! This can give a brutal amount of exp per hours!
Step 1. Put it on T6 & Go to malthael in campaign (ONLY WORKS T6 CAMPAIGN)
Step 2. Kill him.
Step 3. Watch the exp (quest reward will be bugged) and you will recieve 243 million exp if you've got the exp bonus.
The Furnace is almost a must for this since it basically oneshots the boss.
There's a community where people post when they're at the boss called: MalthaelFarming and you can check it out for more efficient farming!