Ran into that parallax problem now and then. In 1995 they sent me a new variable once for a big game hunt I was planning, as I recall a 3-9x or so, and the only magnification where there wasn't any parallax was the top end. I tend to prefer magnification somewhere in the middle of that for most big game hunting, so told 'em what was happening. They said that's just the way things are--apparently due to the brass erector tube. It wasn't too long afterward that they started revamping the line-up--without the brass tubes.
Good hunting, John
On the HBRII I disassembled, the reticle lens cell had two lenses. One lens had the horizontal cross hair and dot on it. The other lens had the vertical cross hair on it and fitted against each other in the brass ring that supported them. Evidently the small gap created from the thickness of the wires/dot manifested as the parallax issue. You could eliminate the horizontal parallax, you could eliminate the vertical parallax...but you could never clear both horizontal and vertical at the same time. This remained a constant at any of the yardages we shot at (100-200-300) or in any lighting condition.
It's amazing that scopes work as well as they do.....
-Al