QoS is a bad word.
Control freaks love QoS.
They can debug it themselves.
People who have are held to SLAs operating production networks have better things to waste their time on, and better ways to crash their switches.
"But I'm not running IPv6!" That means you actually are, and are nor longer in control of your network.
"I will block IPv6!". Say goodbye to all the grants that pay your salary. And everyone's desktops and devices will just make tunnels anyway.
Say NAT one more time, I dare you.
If you think that NAT is protecting you, let me know who you are, so I can blackhole your address range and your IS.
Turning off v4 ICMP is just stupid.
There are lots of stupid people.
You cannot turn off icmp6.
There is no frag in v6.
Thus mtu detect must be on.
Thus icmp6 must be on.
Live with it.
dhcp6 is port 547 not 67