It's pure RNG, honestly. Rather than farm for hours expecting a drop, break it up. Farm an hour here, an hour there, and make sure to start party finders with strict requirements so that you get several clean, quick clears. When I PF on the weekend I set a high iLevel, set it up for single tank/single heal, and state that we're clearing before Swift Liberation. If we don't, then I disband.

Bismarck requirements are less strict, but you still need a good party for multiple quick clears and again, solo heal if you can manage it.

I'm frustrated because getting a competent Thordan party together on my server is near impossible.