It surprises me that Material Design's solution to a required field is a slap-on-the-wrist after failing to fill it in rather than letting the user know ahead of time. It reminds me of those sites that yell at you after you choose an ill-formed password without telling you ahead of time which highly specific format is required: anger-inducing, as well as time-wasting.
I, like Stephen, am working with a form-driven site, in my case for an insurance company, and a given page can easily have 20+ fields. (Ever gone through a home quote?) Some fields are not required. I'd love to get rid of them, but they are part of a business requirement.
Putting "(required)" at the end of the hint text each required field makes the form appear absolutely littered by them. I ended up preceding the hint text of required fields with the asterisk, and keeping the asterisk around after the hint text goes away upon entry. Looks decent, and - more importantly - tests well.
Also, if a specific format is required for entry, I do what MD does after the user makes a mistake (pictured in the thread above), but I also display the same message upon focus, using the focus color for the text instead of red. Works out nicely.