I have studied German on and off since high school, including at college and with a private tutor (an extremely urbane and cultured professor of languages from Johannes-Gutenberg Universität Mainz while stationed in Germany), as well as having spoken rudimentary German while living in Germany and having read various German materials. I'm now polishing my skills with Fluenz German, and I have encountered an unfamiliar usage.
I do not recall ever having heard, or read, the articles/relative pronouns der, die, and das used as personal pronouns rather than er, sie, and es, as in "Wo ist der Dom?" "Der ist da drüben," as the construction appears in Fluenz German. I would always have said, and expected to be told, "ER is da drüben." Is this usage by Fluenz an uncommon one, used here in order to simplify things, that a native speaker of German would understand but not ordinarily use? If it's the more common usage, does it reflect a recent trend in German usage away from er/sie/es?