Applied online. About 2 weeks later received an inline interview. Being interviewed by a computer and not a person is a little awkward. But I guess not that awkward since I got another interview. The next one was insane. Spoke to 5 different people that ranged from 2 years - 18 years experience. The interviews were casual but 3.5 hours long and then a brief assessment test to see how you examine and problem solve. It was a bit over whelming.

15min hirevue with pretty base level questions, know why you want to work at Mercer. After that, 1.5 hr interview with four consultants (2 per 45 min). Lots of questions based on your past experiences, why Mercer, etc.