During my >500 segments with Finnair, I have not been influenced by strikes a single time, so I would not say that the strike-related problems are that common. In contrast, I have been influenced by strikes multiple times both with Lufthansa and with SAS. Regardless of that, I still consider e.g. Denmark (the primary source of SAS strike problems) a happy country. Also, I still keep on booking with Lufthansa (and sometimes even with SAS) and do not regard them as specifically unreliable airlines.