All helpers will get a copy each, so the order doesn't matter. The client will receive multiple replies, even multiplied again if you have two routers with VRRP etc. It is common to see four DHCPOFFERs for each DHCPDISCOVER. The client will choose one (often the first) reply to use in it's DHCPREQUEST. The rest is, as we say, unicast (not history)!
