I've previously posted an article to farming Arcanist Doan. Well here is an upgraded version using a hunter and a mage. This strategy is much more effective but requires 2 players. You're both required to be at least level 54 or if you're well geared and think you're an awesome player then probably level 50 should work fine.

To start, enter through Scarlet Monastery library side. The mage needs to enter first and make yourself through the mobs. The mage is good because you can blink around them. You can easily teleport from one side of a mob to another mob with your blink ability. Once you've received Arcanist Doan you'll need to wait for the hunter to get through.

The hunter starts little bit after the mage starts. Once you've entered, turn on your aspect of monkey. It will help you dodge enemy strikes oftenly. When you get some mobs on you, just run through and feign death. That's it, they're all are cheated and you can wait for cool down and make your way through the guards again until you get to Arcanist Doan. Killing Arcanist Doan should be a piece of cake with two players. Just be sure to avoid detonation when he casts it. As mentioned on the previous guide, flee back before he casts and charge back at him when hes over. One of you should be an enchanter to maximize your profits.

He drops 2 blue items, which disenchants in shard that could be sold for 6 gold pieces each, its about 12 gold per one run. Blizzard created an anti-instance farming system that only allows you to do 5 runs per hour, which is equivalent to 60 gold. Divide that with your friend and you'll still get a good 30 gold pieces for yourself. The previous guide listed with the Rogue can get you about 20 gold pieces per hour. This one is 33% more effective.