Mmmh, I am uncertain about the actual topology of that routers WANaccess port. Looking at https://wiki.openwrt.org/toh/linksys/wrt_ac_series it seems like all ports go through a switch. Could you try to reduce the rates to 50% of what you measure without sqm an retest? Also could you please post the output of the foolwing commands on your router's command line:
- cat /etc/config/sqm
- tc -d qdisc
- /etc/init.d/sqm stop ; SQM_VERBOSITY_MAX=8 /etc/init.d/sqm start
This all seems a bit sub optimal, but I have no real idea what is going wrong. And it could be buffering in the switch (which I believe was the initial bufferbloat phenotype) or sqm simply not issueing the right commands, so the diagnostics I asked for might help in figuring our which avenue to follow..
Best Regards