-Witch Doctor, contrary to belief, isn't a straight forward class. Just look at pre-level 40 where you can live forever just by stacking Health Globe drop type moves. This Class calls for loopholes and trickiness. We are not barbarians that just run into combat, cmon now..
-Mana is the most important thing, period. 1 spell that can generate a heal costs about 100 mana... and that 100 mana will lead to about 7k-10k health healed at level 45. Not many things should be used to siphon life, as a good witch doctor should have already learned tactics to not take damage, Period.
-Believe it or not, your pets are #1. There are many builds out there with no pets involved. I find this stupid. People like to think other Buffs and such are better, I've learned that 4 tanks is the ultimate route to success.
1) Soul Harvest your enemies
2) Locust Swarm your enemies
3) Spirit Walk to behind your enemies for optimal pet distraction
4) Locust Swarm your enemies again if needed (from the other side, whatever...)
5) Zombie Charger SPAM SPAM SPAM BOOM BOOM BOOM
This will give you enough mana to Spam with literally never ever losing more than 50% of your mana. Use Soul Harvest if your health becomes questionable, Spirit walk gets you out of anything and regens 30%+ mana. Keep Garg and Dogs on cooldown always.
Ive changed Zombie Bears into Exploding Beasts so younger levels can harness this too, but this build has lead me through everything without a single problem and minimal deaths.