Hi Hannah,
I was wondering, if I get what you are saying, you'd like to create a way to asses your students while they are not influenced by other students responses right?
Have you ever thought of using an a online voting system ? In this sense you would be able to ask your students different types of questions (essays, open questions, multiple choice questions, numerical questions,...) and they would be able to answer to these question in a given time or at they own pace. The polling system offered by Wooclap is super awesome and easy to use for that! The students even have a chat to ask you questions! And they wouldn't be influenced by other student's responses.
What's more, you can even download questionnaires or list of questions from Moodle into Wooclap and vice versa!
Or solution also integrate your day to day tools that you use for class presentation such as pdf, powerpoint, keynotes, google slides,...
Check it out it might interest you!