You mean passing to the task a number of seeds equal to the number of the sources in the given block?
But there is still the issue of the dependence on the number of tasks. If I change the parameter concurrent_tasks in openquake.cfg I can generate more or less tasks, and the random numbers generated are different.
We never did any study on the dependency of the numbers from such parameters, even if in my opinion this is ESSENTIAL. How many iterations do we need to keep this dependence small? Currently we have no idea. In particular the event_loss_table is so sensible to small variations that I am very pessimistic we can trust those results.