Epic's interview process is long but not necessarily hard if you know what to expect. Doing my research on Glassdoor paid off, so I hope this helps someone else!
The best advice I can give for the whole process is to talk a lot and ask questions - real questions about things that concern you (that high turnover though) are okay, because it shows you're seriously considering the position. Be sincerely engaged. Also, go out to dinner with the Epic employee the night before. Mine answered my questions candidly and was very helpful.
I submitted my resume to a recruiter at my college career fair and filled out an online form. A couple days later, I had an email to set up a phone interview for the following week and took a brief personality quiz. After that, it was a skill assessment in logic, reasoning, and programming. After that, they flew me in for an on-site interview. Everyone was extremely friendly and available through the whole process.
Phone interview: Super chill, 20-30 min. Your interviewer will walk through your resume with some questions about your experience. Be ready to answer why are you interested in working at Epic and/or in the healthcare tech industry. Most importantly, half the interview is set aside for YOU to ask questions. Take advantage of this and show your interest!
Skill assessment: Not chill, 3 hours. Definitely the rough part of the interview process. Honestly, you'll either be good at it or you won't, so don't stress out about studying. The programming test seems crazy hard, but I have 0 experience in programming and passed. They mostly want to see if you can pick up new things quickly and think logically. Not everyone's cup of tea.
On-site: 1) 10 min presentation over literally anything. I choice a topic that was not technical or business-related at all - Epic's culture is quirky, so geeing out about something interesting for 10 minutes probably worked in my favor. 2) Case study. Not at all like scary consulting case studies, more ethical and customer-service related. If you have common sense, you'll be fine. 3) PM interview. Questions about your leadership style, work ethic, dealing with difficult people, and giving/receiving criticism. 4) HR interview. You'll bring a list of 3 references - be prepared to give a good and bad thing they would each say about you. More behavioral questions. They'll ask for salary expectations. 5) Lunch and a tour - not a formal interview, but stay friendly and interact with your group.