For those of you that might not be aware, the current version of D.Va's Defense Matrix doesn't block shots until they are a certain distance away from the muzzle of the gun that fired them. This might seem insignificant, but in reality its a massive issue since D.Va cannot prevent Roadhog's hook & one-shot combo or Zarya's ult if she fires it straight into the ground, even if the Defense Matrix is covering both heroes entirely.
Thankfully, this little annoyance is going to getting fixed in an upcoming patch, as noted by Overwatch's Principal Designer Geoff Goodman. If you're interested in the details, here's the full quote:
"This is excellent feedback, thank you.
I just tested it to make sure you could project defensive matrix through an ally to block shots on the other side, and you can. If you can find situations where this doesn't work it would be great to hear or even better, if you have a video showing it it would be helpful, since it would be considered a bug.
That said, there is a change coming to defense matrix next patch that you guys might be interested in. Currently on live, defense matrix wont block shots until they are a very small distance away from the muzzle of the gun that shot them. Generally speaking players wont notice this effect, but it matters a lot in certain situations, such as blocking an ally from getting killed by a roadhog hook combo.
Next patch the plan is to remove this minimum distance so the projectiles are killed directly out of the muzzle. This means it should be possible to save an ally from a Roadhog hook by covering them with your defense matrix, which doesn't work on live right now."
On a slight side note, its also worth mentioning that the upcoming patch will bring with it some much-needed balance changes to everyone's favorite murderbot Bastion. You can find all of the details by heading over here, but just don't expect to see an official release date as the only thing we know is that the patch is "coming soon".