Your passive abilities will only serve to strengthen the pets that defend you even more. Circle of Life will help you build up the number of Zombie Dogs protecting you. Over time you should be able to replace most of the lost dogs with new ones. Zombie Handler makes it possible to start with four dogs which will make farming easier and more manageable. Fierce loyalty is your last passive ability and it will really help keep your pets alive over the long term. With your life regeneration your pets can rejuvenate between battles. The longer they live, the more mana you have to spend on damage spells and the faster you can farm.
Diablo 3 Witch Doctor Gem Selection
The most important gem to your farming efforts is the topaz gem because it will boost your chances of finding rare items. Since item drops are completely random the best way to get better items is to get as many possible magical drops as possible. With the best Topaz gems you will see more items and have better odds at finding something great.
Place emerald gems in your weapon sockets to maximize your farming ability. Since your character will be dealing a series of slow but powerful spells the best way to take advantage of that damage is to increase your odds of getting a critical hit. When you do you will have a huge boost of damage that will overshadow the small amount you would get from a ruby.