While I was referencing a guide site on my first Huskar play, I did put additional levels into Burning Spear in the late game. That was pretty much because I had nowhere but attributes to put it in, though. It did more damage then, but it never seemed to amount to what other heroes were doing. My guess as to why they recommend 1 pt: While it might not be a complete waste, it's also not a top-tier attack modifier like Clinkz, Drow or Silencer have. Plus, they recommend going for lifesteal thru Helm of the Dominator, and the extra skill points help you raise other abilities faster. Just a guess.