At first I thought the soldiers were just not having their damage reduced when multiple were attacking the same target. This is obviously quite strong on him, but it couldn't be why he was god-like.
When you have multiple soldiers out and you ult right on top of someone, I'm pretty sure it keeps applying the ult damage for every attack as long as the phalanx soldiers are on top of your target. Not sure if it applies that ult damage for each soldier.
-> I just did baron when each soldier did a bit over 200, the attacks did 600 with 3 soldiers, but when i did the ult with it, every attack did almost 2000 damage. which would be 1400 bonus/3=over 400(prob around where the ult damage was. So with that math is guess the ult damage is procing for **every** soldier that is attacking next to it.
And that is why everyone is getting one-shot right now.