Looking at NCAA numbers to determine he is a bust is ridiculous. Keep mind:
1. He will still be playing on a defense first team.
2. The team is losing 3 of their top 6 scorers.
You combine #2 with losing Gillies and the team is likely going to be about as offensive as a Sunday school class.
He's going to be a senior (a young senior, but a senior nonetheless), who has a set of physical tools that are far better than the average NCAA Div 1 player. He should be close to (or over) 200 lbs playing weight by next season, as well.
All excuses aside, I'm not asking him to challenge for the Hobey Baker, or put up outrageous numbers. Near point-per-game for a forward in his senior year - even junior year, if you want to compare Jankowski to other guys the same age - is pretty much a bare minimum expectation for a prospective NHLer.
If Jankowski puts up another season of 25-30 points in his senior year and does become anything other than a fringe NHLer, he'll be a massive outlier. All of the "late developing" NHLers I can think of could put up at least 35ish points in their junior and senior years, including Colborne, Wheeler, Kreider, etc.
edit: Actually, I'll give him this: if he leads his team in scoring by, say, 25%+ over the next guy, but his numbers haven't improved, then maybe we can say he's continuing to develop into a potential NHLer and is just on the worst offensive team in the NCAA. But if he's just part of a big group of offensive mediocrity, or worse, gets bypassed by younger guys on his team, I'm throwing in the Jankowski towel entirely and will gladly eat all of the crow you can serve if he actually becomes a useful NHLer.