LB Traffic and OAM traffic isolation

What type of traffic are you seeing that going via the mgmt interface ?

The only processes that can see the management interface are those running in linux (such as the bigd health monitor process, ldapsearch, ntp, or the management GUI). Even for those processes, they will prefer a tmm route before they use the management default route, unless you've also specified a management-route to override that.

Load balanced (tmm) traffic can not access the management interface, so you can not have user traffic arriving at a virtual server, and then being load balanced out through the managment interface.