And how do you compare the value of a top offensive prospect with a top defenceman prospect? Teams draft based on their individual needs. St. Louis obviously passed over some of the more offensive-minded prospects because they feel that they can benefit more from a Pronger-type player in their lineup.
You obviously have no idea how teams put together draft lists - consideration of their individual needs is *way* down the list of factors that go into deciding who they're going to take in a draft. If they're indifferent between two players, then
maybe it's taken into consideration - but in 99.99% of the decision making, current need (or even perceived future need) is *never* a factor.
St. Louis took Erik Johnson because they think when all is said and done, Johnson will have the greatest impact of any player in the draft. Remember - scouts stated that he reminded them of Chris Pronger at the same age. The words "franchise defenseman" were used when describing him. Yes, guys like Kessel, Staal, Backstrom, Toews, Little, and so on will probably end up having better offensive numbers - but
no one who ranked the 2006 draft class after January had Erik Johnson rated #2 or lower.
They didn't select Johnson because there was a hole on defense and he could eventually fill it - they selected him because they believed that when all is said and done, EJ will have the greatest NHL impact of any player in the 2006 draft class. That's how I prefer to look back at drafts - not just, "ooh, who's put up the best numbers in the 7 months since the draft?" If the Blues believed that Phil Kessel would have the greatest upside of any player in the draft, they would have taken him. They didn't.
If you think I'm off base, go find posts made by steblick where he constantly points out that teams rank players based on (A) potential upside, and (B) likelihood of ever playing in the NHL, and that current or future need is almost never part of the decision making process.