Yeah, that's what they say. Honestly, though, it was only a problem if one team had a competent Mercy and the other didn't. And she's not all that defenseless, that little popgun of hers is no joke. She's just an easy target when she's actually healing if her team doesn't stay reasonably close to her. After all, a healer needs a decent meat shield. In the great words of Sarge: "Just because your bones are broken, doesn't mean they won't stop bullets from hitting me!"