ISE is not required but does make assigning SGTs to an Access_accept incredibly easy. You can assign tags in a few ways. 1. Statically to a switchport or an SSID, dynamically via RADIUS av-pair, and in the near future, you will be able to create Network Object Groups and map them to SGTs as a fallback tagging mechanism.
CCIEw# 45253 / CWNE# 249 / Senior Technical Marketing Engineer - Meraki MS Product