If Skullbasher worked on Facless Void or Slardar, would it actually be OP?

I was just thinking about it. Sure it sounds strong to have the infinite bash, but realistically the gold
they would be spending on skullbasher could instead just be spent on attack speed for more bash efficiency since they would still have pretty poor attack speed, or that gold could be spent on getting more crucial items like BKB. I dont think either Hero would ever rush skullbasher and both are fully capable of perma bashing in the late game anyway. Do you think Skullbasher being disabled on them is a remnant of past balance or would it still be too strong?