Nope, I played against Octo normally.
Octo Mark I can only use 1 weapon without energy for range 4 - 9.
As you see in the screenshot I simply drained it and then fired away in range 4 - 6.
When I was pushed to range 7 I moved back to range 4 and fired again.
Octo fired the whole time his energy free top weapon and then cooled down cause I was out of range for the other energy free weapons.