I personally don't find playing a DPS class any less pressure than other roles. Sure in a lot of content you can play half assed and get away with it but really the same can be said for any role in those situations. For content that there is pressure to perform well all jobs have equal responsibility and are noticed if under performing.

Now on a personal level you may feel that a particular role is less stressful but that's more based on your preferences than any of us on the forums telling you one is less pressure than another. I personally find healing is least stressful in progression content than tanking or dpsing. But that's due to my comfort level with the job and role more than it being mechanically less of a lynch pin for the group.