DPS: The main source of damage with this build is Rain of Toads. Unlike it's unruned counterpart (Plague of Toads) RoT is a dependable, short lived, high DoT. Grasp of The Dead (Groping Eels) is also a cheap, but effective DoT that has snaring capabilities.
Regen/Resource: At first glance some might think Spirit Barrage's (If the Spirit is Willing) purpose is to also be a DPS skill. Wrong. The only purpose of SB in this build is to be used in conjunction with Rush of Essence. RoE + SB + Golden Rune = Very high mana recovery capabilities.
Survivability: Here is what I see lacking in a lot of other builds that have come before mine. From my understanding based on what I've seen (official gameplay vids, unofficial vids, leaked PvP vids), the WitchDoctor is almost/ just as soft as the Wizard. Jungle Fortitude is great passive that strait up reduces damage taken by 20%, but the real survivability in this build lies with with ZombieDogs modified with an Indigo rune to make Life Link (40% dmg absorption @ rank 4, 70% @ rank 7). With this combo of JF and ZD/LL, you won't be that guy in the party that always dies in one hit (D2 Reference). The Gargantuan is there for the sole purpose of tanking.
Yea the dmg might not be amazing, but it's more the mana costs I'm worried about. I could choose Firebats (Direbats or Hungrybats) over Rain of Toads, but bats costs a lot more to maintain. When you compare the mana costs:
1 cast of Direbats (long raged, channeled) = 295 mana / 208% Damage
1 cast of Hungrybats (short ranged, channeled) = 295 mana / 273% Damage
1 cast of RoT (short ranged, long ranged, AoE, spamable) = 355 mana (costing only 50 more mana) / 286% Damage
Do Firebats do more damage over time than RoT?: Yes
Do Firebats cost a hell of a lot more to maintain?: Absolutely
As for this build having "mana problems", @ rank 4 Spirit Barrage only gives back 59 mana per hit, (along with 29 mana per second for 10 seconds). At rand 7, I'd receive a net total of 280 mana per hit using SB. Use it 3 times, I'd get back 840 mana + 90 mana a second. That in itself would almost completely remove the need for gear that increases mana regeneration allowing the player to focus on equipping other gear that boosts magic find or damage.
Oh no no no no....haha. You're very mistaken. My guess is that you've looking at the beta gameplay videos and thinking that mana is going to regen at relatively rate when the Witch Doctor achieves higher levels later in game.
(Brief Summary) Mana regeneration does not increase with level. At level 1 the WD has a regeneration rate of 60 mana per second and poison dart only costs 30. The only things that increase with level are spell damage and mana costs. At level 60 the WD has 3250 total mana, but still has the same base regeneration rate of only 60 mana per second.
"At level 60, it would take almost 5 seconds before you regen the mana [Poison Dart] just used."
I know it's of terrible quality, but notice that he runs out of mana.... ironically only using Poison Dart. Also notice that the skills that he's using to help him regen mana are Rush of Essence + Spirit Barrage.