[3.0] Spectre Summoner - Newbie asking for insight

Hi, since reaching Act 9 I've had my eyes set on a spectre summoner for this league. Problem is, I've never really made one, and with the changes to energy shield I feel very lost when trying to figure out which items or what kind of tree would be the most optimal for my build.

Without going into great detail, what I would like to achieve would be the greatest amount of damage/survivability with the greatest amount of spectres possible, using Sandworm Slaves (Vastiri desert).
I could run around with 6 spectres, but I would sacrifice a lot of defence since this requires midnight bargain(s). This might just not be optimal.

What I'm asking for is to understand why I should do x and not y when building this specific spectre summoner. I'll start by asking some major questions of mine. Do not feel obliged to answer all of them.
[EDIT]...it might be important to add that I would like to be able to go for Shaper if I'm skilled enough.


Midnight Bargain - Why/why not?

Would I want more spectres or auras?

Should I even rely on ES as my main defence, and if not, why exactly?

Zombies, SRS, and/or Golem - Necessary?