For Witch Doctor, Pants are mainly chosen from Inna's Pants, Blackthorne's Pants and Rare pants items drops. Which one did you choose for your WD leg part?
Inna's Temperance: +70 Intelligence, +80 Vitality, Attack Speed 9%, +12% Movement Speed, Critical Hit Chance Increased by 1.0%. With Lacuni Prowlers in as the bracers, you can have +24% movement speed now. Then you can choose The Witching Hour as the belt to gain more attack speed and critical hit damage.
Blackthorne's Jousting Mail: +155 Intelligence, +179 Vitality, Each Hit adds +400 Life, +11% Life. The main stats intelligence and vitality can increase greatly with this on legs. Life on Hit stats can even help solve the problem of life shortage in battle.
Rare Pants Drops: +161 Intelligence, +199 Vitality, +61 Resistance to all Elements. If you are hard to survive lower than Monster Power 3, then you should consider rare drops instead of legendary items. If you could farm one with stats like this, it would be so great.
You can find top ones with those stats we have mentioned. Then choose one with the Diablo 3 Gold price you can afford. Of course, you should consider what stats are the most urgent for your class. You can not have both high intelligence and high vitality. They should in a realm. Then you can narrow it down by your other needs. Make full use of Auction House now as AH would be shutdown in 2014.