Lena can see that Jack is still moving, and that's all she really needs to confirm that he's still in the fight. So she doesn't try and focus on what she's doing, instead keeping all of her concentration on holding the attention of the remaining Bastion unit.

She's in the middle of kicking off the wall when the Bastion shifts back to recon mode, effectively swiping her aside in the middle of her dash. Under any other condition, it might have been a lucky swing -- but its not the first time its happened today. Tracer collides with a grunt, and another PING just as it lets off another spray of fire.

Something clips her calf as she moves, but she doesn't stop to address it. If Jack couldn't handle it without the rockets, then she would have to try and bomb it herself before she took another hit like that.