Small update. There seems to be an extreme weakness with the battlenet ranking system. I'm a very, very average player at best and I just secured a position in gold by, apparently, winning 3/2 matches.
I've heard of others dropping into platinum by simply winning all of their placement fights. Oft their opponents were of negligible skill at best.
The system they're employing to rank players feels like it needs a great deal of review. I know I am not one level below world class SC players. So don't be shocked if you play your five placement rounds and end up in platinum XD