What I "fixed" was on the apu2 with the burst/cburst change, I went from completely bottlenecked on one softirq to having 3 eat cpu, and from 400mbps to 900mbps. Now, that's a quad core and the e1000 (?) driver. The edgerouter X is a dual core, and you did see a small improvement in throughput, but I'd hoped for more.