Regardless of what's on the 11R side: if the other side of the connection is non symmetrical, this will automatically "convert" the entire connection to being unsymmetrical. The EPSi doesn't have symmetrical jacks, so the cable connection becomes unsymmetrical anyway. But as long as your cables aren't defect and ground is properly handled you should not have issues whatsoever. Usually it is recommended not to run too long cables if they're not symmetrical but this becomes less important the higher the signal level is. For mics it's very critical, for all instrument levels it can almost be neglected.
The output level of the fx loop of the 11r is definitely high enough to run quite long asymmetrical cables without getting issues.