Agreed with the OP. I don't think the original intent was exactly zombies, but by First Contact they had been basically turned to this. I've always wondered if they weren't intended to be an extreme take on Communism and the like.
No. Not communism. It was on the decline when they debuted (the Berlin Wall fell less than 6 months afterwards, and the USSR less than 2 years later).
I think the Borg were intended more as a commentary as an example of the over dependence on technology, and the blurring of lines between machine and human.