well just add it to both groups on tier 3, it's that simple.
if tier 1 (high packets loss or high latency) it will switch to tier 2.
and if both 1,2 dropped 3 will kick in.
you control which one are primary and secondary with tier numbers.
believe me every day you will find a new reason to love pfsense more. i love it so much
i just installed it on a VPS and configured openvpn on it.
so now i have a personal vpn for 5$/moth.