I'll answer about Berserk, as I've encountered this many times:
If the enemy hero has an artifact that protects against spells affecting the mind, then when attempting to cast such a spell (in particular, Berserk) and the option to display the spell's area of effect ("Cursor Shadow") is enabled, we will see that the enemy units are not highlighted. This is very useful because it helps to understand that the enemy has a corresponding artifact, and to cancel the spell by casting something else.