So I have my ISATAP environment somewhat setup in my lab, my manageout devices are getting a 2002 address but the gateway is still showing fe80. If I manually enter in an IPv6 address and specify the DA's IPv6 address as the gateway, all is good and I can manageout successfully.
Manage Out Device:
Tunnel adapter isatap.contoso.lab:
Connection-specific DNS Suffix . : contoso.lab
IPv6 Address. . . . . . . . . . . : 2002:a8ad:10fc:1:200:5efe:xxx.173.106.50
Link-local IPv6 Address . . . . . : fe80::200:5efe:xxx.173.106.50%13
Default Gateway . . . . . . . . . : fe80::200:5efe:xxx.173.106.41%13