when using load balancing with a pppoe connection and another static or dhcp connection load balancing will never use the pppoe connection due to the way pppoe uses the iptables vs the other connection.
static routes with a different metric does not alleviate this as it would if one connection was dhcp and another static.
issue has persisted since original pull from vyatta codebase
i believe that in edgeos this issue is the primary reason load balancing is handled completely differently.