There are two ways to look at the issue.
1. It is a general attack on gun rights. This is certainly the agenda of some. From sociology and critical criminology, you get the idea of a moral panic - a useful concept.
Some incident ignites a set of folks in government and media to interact and try to use the incident as a vivid cue to push an already existing desired policy program. The country panics and is stampeded towards action. Usually a rational analysis of the action is not part of the debate. Emotion rules. The attack on Iraq by Bush II is an example.
Tucson is a classic case. Outraged politicians and media. The focus on the extended Glock mag as crucial to the problem - not rationally the core of the issue. Banning them would not remove the risk from truly disturbed individuals.
Thus, use the incident to try to promote a true antigun agenda and try to remove guns in general from the public.
2. Did incidents like Tucson or VT for example indicate that there is real problem in NICS reporting that could be fixed and reasonably so. Cho and Loughner certainly gave legit warning signs that debateable could have been in the current system.
Could them being in NICS slow them down or prevent them - no way to know?
However, increased violent potential screening for general firearms purposes might be proposed but has way too many false positives. Current views indicate we have no psych tests that are useful violence predictors. So asking for folks to take psych exams for general firearms ownership (independent of the rights violation, IMHO), wouldn't work. The only predictor is past criminality or threats. So Cho and Loughner might well have been aborted if there were better screening on their overt and threatening behavior.
Such a debate would have to be conducted with experts and not pols, advocates, etc. The latter just throw out emotion and rhetoric.
It is all just posturing. A real look will not occur. IMHO, a combo of truly trying to catch the overt Cho's and Loughner's based on real threatening behavior and a realistic policy of encouraging responsible carry would be in MY report - when I am invited to write for Wayne, Charlie, Larry, and Barrack.