Need help: Zombie Meat Shield and ballista damage

hello, I am still new to the game, and I would greatly appreciate any suggestion or help to formulate this build, I know a few more guys who like the idea too, but I imagine this would be a difficult build to even make semi-viable.

Main Idea: get an army of meat shields to tank, lay down a line of ballista and watch mob and boss get shred to pieces. Minimum investment on minions to make them tanky enough, and focus on balista

what I am looking for:
This is more aimed as a fun build and does not need to beat the end game bosses, and doesn't need crazy clearing speed.

Reasons behind the build: I am a engineer in real life, and seeing these amazing giant magic-mechanical Autocrossbow firing away just makes me happy.
I got sick and tired of spamming cluster arrow from turrets in diablo (really loved it in the begining), and got sick and tired to just walk around and everything around me dies to my specter and don't have to do a single thing (fell a sleep once, haha). So I decided, why not do both

Issues I can see:
How to balance the investment?
Invest in both will inevitably reduce efficiency, and all these games specializing and spamming a single skill (or an aspect such as minions) is always more effective. It would be hard to figure how much to invest in both.

How to take care of survival?
Just CWTD immortal call will help against physical, but this build will probably have weak elemental resist, and character will die a lot from elite or boss that spam AOE elemental attack.


again, would really appreciate any help