Jesus Christ a person who dislikes Phantasialand!
Slagharen has a fab little dark ride, but that's all you missed, besides, only one other park on the same day? Pfft, I did 4 when I did Slagharen (and it DOES annoy me that I have to revisit)... But trying to do not even half a day at Phannyland is ridiculous at the best of times, let alone a big event day...
It's definitely a culture thing, and probably works better given that the parks tend to be open for decent periods during busy days...