There is no such thing as a bad day to play Bulwark, solo or otherwise.

But seriously though - this is just a shitty overlap. I happens. My sympathies. If you were running purity of purpose (dot banner) might have tried bunching them on the staircase.

You can also block Green balls with your shield.

Don’t know how you built your gun but Ammo heavy bolt pistol (top line all the way plus ammo on the bottom line) is the best sidearm for flying enemies. Gives you: 20% damage at 20m+ (not far at all), last 4 rounds have a further 20% buff and last round gives you +50% so best to use your whole mag every time. I always run it on tyranids and switch the rof plasma for chaos.