Those systems will not max out a 10Gb link. SnapMirror is not designed to be a super high transfer of data, but more in the background. With BRE throttling it will be even slower so it doesn't use all CPU resources from frontend ops.
Was your system sold to be able to do 10Gb SnapMirror throughput or sized for that? What is the expected speed?
Also, if your disk usage is 80-90% busy, more than likely you don't have the headroom on your disks to move data very fast.
If it really is a concern, please open a case and we can help direct things, also check network for things like packet loss.