I think there is a little more to the process than above. Multiple nominations will slightly increase your WCS which matters as you compete in the different "buckets". You will compete on the primary slate for each nomination source. If you have the highest WCS for any one of those slates then you will get an appointment. If after all the slates are resolved, you did not "win" one you are placed on the NWL. The top 150 or so candidates from that list are then offered appointments. That 150 number is an estimate and moves up or down depending on many other factors each year. So the short answer is yes, multiple nominations increase your chance of an appointment because you have more opportunities to compete for an appointment.