Not dropping ICMP when simple queue limit is met.

When a customer meets the upper limit of their simple queue is there a way to prioritize ICMP, at present the queues fill up and then drops packets. This to a third party looks like their link is dropping, when in reality they are just hammering their connection. I have already created mangle rules to mark ICMP. How would I make sure these packets get through so a MTR looks stable?
2 X chain=input action=log protocol=icmp log-prefix=“PING”

4 X chain=prerouting action=mark-packet new-packet-mark=ICMP passthrough=yes protocol=icmp

5 chain=input action=mark-packet new-packet-mark=ICMP2 passthrough=yes protocol=icmp

6 chain=output action=mark-packet new-packet-mark=ICMP3 passthrough=yes protocol=icmp

7 chain=forward action=mark-packet new-packet-mark=ICMP4 passthrough=yes protocol=icmp