Not depend on the rate of BTC. eg Darkcoin grows
The overall CC market trend tends to go as BTC goes (see charts), since it isn't absolute you will find anomalies. One should not focus on the anomaly for guidance or explanation about the overall market, much less any specific cryptocurrency performance.
EMC2's rate is low now because it was forced down before the overall crash and efforts to force it back up only yielded what we now have.