Haunt is basically like a ranged rend and leave the monk at low chances to reach 5 points ahead of the witchdoctor.
Withch doctor still has several kit's that can be used as a better damage output than haunt but it will not be so simple and straightforward to use, aswell as impossible to avoid
Tbone do you allready use WC and TS, if yes it leaves you short of one spell of mobility in your choice.
IF you only do use WC; TS will apply similar mitigation aswell as slow and the same regeneration, the difference being that you must be aware and able to apply it to ur opponent.
As for items / skills , in my opinion the most important thing is clever and strategic builds versus every oppononent becuase stats should leave you at a minor increase compared to what every player should be able to acquire over some time.
And i think perfect billion dollah gear, leaves you small advantages versus a ' Good gear set' that any a smart and dedicated player will in the end round up towards.