While I don't recall any leaks specific to piracy investigations, there were numerous leaks proving NSA involvement in cases which could in no way be described as relating to terrorism.
Off the top of my head:
- NSA surveillance of the semi-public Brazilian oil company Petrobras: http://g1.globo.com/fantastico/noticia/2013/09/nsa-documents...
- NSA tapped the phone of German Chancellor Angela Merkel: http://www.spiegel.de/international/world/merkel-calls-obama...
- NSA spying of Indian diplomats to uncover details about their nuclear and space programs: http://www.thehindu.com/news/national/india-among-top-target...
This article is a decent compilation of Snowden-related stories from the first year after his leaks: http://www.businessinsider.com/snowden-leaks-timeline-2016-9