I think I find tanking intimidating because of being out in front and initiating pulls, so I feel self-conscious and worry if I'm going too fast or too slow or positioning the mobs poorly. DPS and healing are more reactive--you hit what the tank pulls or heal the damage they take--and that feels less pressuring to me.

I hope FFXIV gets cross server grouping soon! WoW has had that for a long time and it's sooooo helpful not having to deal with friends being stuck on different servers anymore.