There is a heavy importance on using units with elemental advantage against the bosses you are farming. You can check the element they are weak to when selecting the boss in the Anomaly interception menu.
These are the 5 Bosses currently available to challenge in Anomaly Interception:
All of them will also drop Custom Module
Custom Module Description A small machine that can tamper with various operating systems for all sorts of devices. Contains a labyrinth of circuitry inside. Don't try to take it apart unless you know what you're doing. It can be used as material for modifying equipment. .
The boss will also deal increased damage to the weak element by a whooping 300%, meaning you really need to plan your teams for Anomaly Interception.
In terms of overall difficulty, the bosses themselves have slightly different mechanics (closer to the mechanics of the solo raid versions) but not nearly as difficult.
These are just guest approximates as to where you should be able to clear, this does not take into account overall account progression, how well your units are built or if you even have all the recommended units.