This kind of contradicts your post title, and your OP, you say you want to know what the best 70 jack build is and you don’t want to have to rely on your jacks, then you say they are supposed to be meat shields and not die rapidly, well if you want the best build they can be distractions but they need to die rapidly, its just the way it is, and typically the Celestial mod for any character is not going to give way to the best build they have available.
I have tested this build with my friend who created it and I think its fantastic and fun to use. Its fast at killing, great on ammo, and has massive survivability to it.
Below is a gameplay video of his build in action against Eclipse/EOS
Here is a link to his build thread on the forums.
Level 70 Jack Build
Maybe his builds not for you, but you asked for the best, and you said you didn’t want to rely on your jacks.