Is GRE/TOEFL mandatory for an F-1 Visa?

GRE and TOEFL are not mandatory requirements. If your university does not require these, ensure to take a letter from them stating the same to the consular interview.

However, this might trigger a question of your ability to be enrolled in other University’s (presumption of incapability) for which, you have sufficient work experience to say that your requirements matched exactly to the prospective university.

Mainly The consular officer notices three things:

1. If you have sufficient funds and financially stable. 
2. Presumption of immigranting permanently.
3. Are you qualified or have the pre-requisites to take up this course and come back to your home country.