It was widely thought that Krakow was pulled due to it diluting yield on the existing LGW route. I don't know if that was true or not but I used to monitor fares and loadings on that route, among others, and it certainly didn't look as if yield was poor.
I think EDI however was dropped for the reason that LTNman suggests but I would be surprised if DUB couldn't be operated profitably as a double-daily, although again I don't know for sure.