Clara has a 1-hr SLA for the processing of an incoming message. While I cannot give numbers on the speed of annotators (or volume), I can say that our platform is designed to enable quick and accurate work via incentive mechanisms. We avoid fatigue in part by making it easy for CRAs to navigate and work with data. Wrt to overlapping annotator schemes, these are known to be effective. We'll be writing more about how our human backend works in future posts.
Thanks, in the future post would also be interested in the trade offs between building internal system vs. using a 3rd party (maybe you do?) like mechanical turk and the incentive structure.