Here is the build that I use. I've only started endgame content but I ran a 49 expedition with full modifiers and Immortals without any issues.
https://wolcen-universe.com/builds/gjVnzg-necro-tank
Essentially you pop Plagueburst, roll into a group of enemies, lay down Anomaly, and giggle as everything explodes. For longer fights I hold down the "force stop" key and auto attack with a staff while spamming the zombie skills to keep them attacking the boss. Anomaly is used to to suck mobs into one place because when an enemy dies inside Plagueburst, they drop a toxic cloud. Each individual cloud does its own damage, so when you get a giant group together, one thing dies and everything else vanishes in a puff of smoke.
In addition, you can bounce mobs to CC them if you place each Anomaly slightly off center of each other.