Just to throw some numbers out there in support of this:
Assuming your group runs and successfully completes Old Glast Heim daily, and assuming they get around 6 coagulated spell per person per run, it would take (8500+6500)/6 = 2500 days to obtain both cards for each person. Even if your group decides to pool all their spells together, that's still going to take over a year to obtain both cards.
Edit: After running the instance a few times, it seems like each character is guaranteed 2 spells upon successful completion. So my original estimate is even worse.