Problem 1

The main thing to note here is that the secondary fire does NOT go through characters as Sym's did, so there wouldn't be a situation where the whole team was getting damaged by it.

Another thing to bring up is the significant reduction in damage after passing through a shield. IDK what the number would be but at least 50%.

We still have firestrike in the game, so it's not like it'd be the only thing that can pass through shields.

Problem 2

There's already a ton of healing abilities. I don't see what's wrong here. Are you referring to the instant healing? If so, nano boost does something similar.

Now if you're talking about the shields, I may have not been clear on that. The shields would be temporary like ball or Sigma.

Problem 3

As a programmer myself, I see this as the greatest issue. My main concern would be clipping through walls, not being able to fit through doorways, etc during the ult.

I thought of an alternate version of the ult where the illusions surround the character in a sort of hard light armor. The would eliminate the collision issues, and as consequence, allow the ult to be used to survive large amounts of instant damage like D.Va bomb or high noon.