I did basically all the good dark rides by 2PM (3 hours in). It doesn't help I spent two days there earlier this season which I focused on the dark rides, as it was so busy the coasters were busy (Voltron was closed too).Although not ideal I think the difference is although the 'big' rides were not open, there was still a full day of things to do that were open, through the indoor rides and the shows. Unlike a UK merlin park which is unmanageable in such conditions.
We have been fit unlucky too at Europa with snow wiping out all of the big rides. Yet we still have the most amazing and magical day doing everything else but the outdoor coasters.
But yeah Pirates in Batavia and Arthur are great but after one ride each, I was ready to go home and twiddling my thumbs with boredom. I surely couldn't of spent more than 4 hours there without some form of boredom.