Obamacare and severability

Heritage.org:

...Besides the extraordinary number of hours the Court has set aside for the Obamacare argument, of particular note is the 90 minutes alone (50% more than a standard case) for the issue of “severability.”  The issue of severability involves whether the Court must strike down the entire law if it finds any portion of it unconstitutional. That issue is usually included in the standard 60 minutes of any other case. One has to wonder why the Court thinks it is worthy to set aside 90 minutes for nothing other than a legal debate that only comes into play if it rules one portion of the law unconstitutional (most likely, the individual mandate). The obvious answer is that a number of the justices must think the constitutional challenge is strong enough that it is likely to need to decide the issue of severability—and it wants 90 minutes of uninterrupted questioning on that issue.

I think the lack of a severability clause is significant and is likely to lead to a find that the whole act is unconstitutional.  In the case of the mandate to buy insurance, it could be deemed necessary for the rest of the act to be relevant or survive.