This is commonly used in speech, less so in writing. This is usually used somewhat as an exclamation, and has the nuance of being said to yourself. Because of that, it's somewhat informal, however it is also slightly old-fashioned.

From an American English perspective, it's definitely archaic. You could hear it perhaps in a joking way by someone wanting to sound old-fashioned/Shakespearean.

This phrase is seldom used seriously. Instead, it is used humorously or ironically/sarcastically — often to emphasize that some situation is not THAT bad. Example: “Teenagers today are always saying ‘oh, woe is me,’ but they really don’t understand how easy their lives are.”