At time of this writing the Cisco 3850 is not on the supported device list in spite of having the same MIB tree as supported devices.
1. This same situation could occur for many – usually older- devices, not just the 3850 device.
2. The tuning parameters to handle such devices are MAX_BATCH (default 20), SNMP_RETRIES (default 2), and SNMP_TIMEOUT (default 2000 milliseconds). We recommend that the overall performance of the system (discovery and polling) should be observed carefully when changing these parameters.
See KB Article TEC1024587 for more information on the general issue.