Difficult Colleagues: Principals and partners in the "Career" consulting practice in the Northeast are difficult to work with. They have huge egos and are quick to cut down and write off junior staff, who are already at a disadvantage because they do not receive adequate training.
Cut throat environment: If you get burnt out from the stress of working in such a competitive, unforgiving environment, expect to lose your job. Being human is not allowed at Mercer. You have to be a machine and take on several client projects at once to meet your billable hours goal. If you don't meet it because a partner has underbid a project, but you have great reviews from colleagues and clients, you will either get a bad rating (and thus no increase or bonus), or you'll get fired.
Mercer is merciless: Going through a difficult time emotionally? Need to take a leave of absence? Better not tell the insurance company work has anything to do with it. That will get you an immediate denial. Got approved for a leave of absence for stress/mental health reasons? Expect the worst when you return. You are now a pariah because you've shown you are weak. Your days are numbered.