DioField Chronicle bosses have very powerful skills with a wide range of effect, plus they have several health bars to deplete. Status ailments like Poison and Freeze can potentially help you defeat them faster, or at least survive a little longer.
For example, when they are about to use a powerful skill, you can use Shield Bash to try to stun them by canceling said skill. When bosses are constantly summoning swarms of monsters, you can also cast an area-wide debilitating spell like Frostbind and cross your fingers.
However, will your attempts to stun and freeze work?
Can I apply status conditions to The DioField Chronicle bosses?
The chances of hitting status ailments will definitely be lower, but bosses can still be triggered by status ailments.
Note, however, that they gain temporary status immunity against the newly acquired anomaly. A disease state icon with a small silver shield on top will appear below their HP bar to alert you to this. For example, if they were stunned, then they will be immune to stun for a while.
So while it’s not very effective to try to poison them to death, it’s perfectly possible to stun or freeze them when circumstances warrant. Just be sure to bring three people with you that can cause said ailments, as the chances of them not landing are pretty high. The EP is also limited.
Of course, there will be some bosses that will be immune to status ailments in later chapters. You’ll know they’re immune if you see a row of status icons with silver shields attached to their health bar.