Uber crushing blow build for merc?

for a summoner necro, dont have Infinity and Fortitude so my options are,

1. g-face, upped and socketed Hone Sundan ( Shael Shael Amn), Duress: for maximum CB with speed and life steal (from socketed Hone Sundan)

2. gface, Duress, Obedience: if I want a bit more damage but losing life steal and speed

3. Andy visage/ Tal Mask, Duress, Obedience: Sacrifice some CB by having life steal, no boost on speed

4. G-face, Treachery, upped and socketed HS: good CB and super speed, also some life steal, seem to be an all rounder

there are some other combinations out of these, but mainly I want to find a sweet spot among CB, attack speed and life steal purely for Ubers, keep in mind, I'm a summon necro (with HOTO and CTA) I have other meat shield and CB Revive source.

"Sweet Spot" is about right.

Personally, I'd go with something along the lines of a Cham'd Vampire Gaze, Duress or Fort and then probably Obedience, upped Hone Sundan or Infinity or maybe even Pride. Though admittedly, I haven't calculated or experimented with summon nec weapons in a while. You do want some open wounds as well so if you go with Fort over Duress, that'll need to be part of the weapon.
Res may require a pre-proc Treachery or the like.

The thing about crushing blow is you want a fair bit of it to take them low asap but you don't want to Sacrifice too much of your normal dmg for it because otherwise you will take too long on what's left of their life after crushing stops having a real impact.

Urdar revives do bring their own crushing so you don't have to go all out on your merc as he isn't the only source of it.