How do straight pull rifles like the Blaser R8 deal with the expanded case that has just been fired? In bolt action rifles the lift of the bolt handle cams the bolt backwards to free the stuck hot case from the chamber. But since R8 and other straight pull rifles don't have that, do they requires a powerful initial pull to free the case?

I tend to load "hot", and have yet to have any extraction issues with my R8's.
Our temperatures here in southern Alberta can vary from -30 to the mid 20's C during the hunting seasons. I like to play at the rifle range even in mid summer, when it can be hovering in the 30 C range, and although the heat reflects on the POI, I haven't had any extraction issues there either!

I load for maximum accuracy which means that sometimes the load is near the top of what is recommended. Thus far, I've never had problems extracting a case with my R 93.

the case has long ago shrunk back down before you get your hand anywhere near the bolt handle.