I agree. I am at a loss to explain why some of the federal laws (the NFA, the GCA, the AWB) were not challenged as violating the second amendment. With the exception of Miller, not one lawsuit.
First of all "Miller" was not a lawsuit, it arose out a criminal prosecution, with Miller and Layton being the object. The trial court through out the indictment, because the law in question violated the Constitution, and thus was not a law at all.
There have been numerous cases since then, here's a sampling of Supreme Court cases touching on the issue (not every case on the list is post NFA as some bear on state laws, the "other Miller" for example), and Other court cases (not all of them federal)>
There have been many cases, not lawsuits, which are civil actions, where the Supreme Court refused to "grant cert" that is hear the cases, leaving the lower court ruling stand without creating national precedent or deciding the issue one way or another. They generally don't give there reasoning for doing so. IMHO they are ducking the cases, but that is only an opinion. Not all of the cases linked above, or even most of them, bear directly on the meaning and applicability of the Second Amendment, but all bear on "gun laws" of one sort or another.
Two examples of denial of cert, both fairly recent, are Silveria (9th circuit) and Emerson (5th Circuit).