Virginia had practically no contest, so low voter turn out is expected. In LA, Mitt did not do much activity, so Rick was sure to win, and that dampens turnout.
However in hotly contested states such as MI, OH, FL had to have good turnout, if the article is correct.
Turnout definitely looks like it’s on an uptrend. To really do a proper analysis, you need to differentiate when a state had a caucus or primary last time and switched to the other this time. Caucuses mean lower turnout. You also need to adjust for population. But Louisiana was up a double digit percentage in turnout.
156,101 in LA in 2008.
186,377 in LA in 2012.