They randomly use "him" and/or "her" in articles. No big deal, yeesh.
There's some truth to the stereotype (there've been dozens of polls on here and they all match the most healers = girls thing, not to mention personal experience) but it will never ever be true for everyone. I'm a dude and I love healing. I knew a girl IRL who main tanked Firelands. There will always be people who break the stereotype.
Bottom line articles randomly use him/her. One Blizzard article about mages said "she" for example. Not a big deal.