When should the dependency from a Drupal core module be explicit? The Standard profile declares the Node module as one of the modules it requires, and so does the Minimal profile. That is not true for the History module, which is required from the former but not the latter.

When should I declare my module as depending from a Drupal core module? Should I assume the installation profile / distribution always requires the module from which my module depends?
As in all versions of Drupal, if your module depends on another module, you should always explicitly declare it as a dependency.