So it appears that Marvell pushed a bunch of patches to OpenWRT on
Christmas, and as a result, trunk OpenWRT (kernel 3.18) can run, and run
pretty well, on the 1900AC.

https://forum.openwrt.org/viewtopic.php?pid=258634#p258634

dual-core 1.2GHz ARM.  Given my experience with processors like the iMX 6,
this should be light-years ahead of the WNDR3800 in terms of CPU
performance.  Perhaps this will let the sqm scripts go well above 100Mbps?

-Aaron