I just ran into a similar problem with my XiTone using either XLR or 1/4 inputs. I had the XiTone checked out and the very capable tech I used told me there was 'nothing wrong' with it. I brought my AX8 in, connected it & was able to replicate my problem and they eventually came to the conclusion I needed to connect either a line isolator, or a DI box (which does the same thing) in between the AX8 out and the XiTone in. I went with a Radial IC-1 Icecube (which is XLR only) and it solved my problem. I tried some of my other DI boxes and they also resolved the issue, but they lowered my output. Probably because they were not particularly high quality DI boxes. The Radial fixed that too. Very transparent in every way that matters.
My symptoms were identical to what you describe too. I could connect other modelers to my XiTone and they did not produce the hum, but the AX8 did regardless of whether I used 1/4" or XLR. I never got this hum when I had used my other powered FRFR monitors with my AX8 - only with the XiTone - which was why I took the XiTone to the shop. Ultimately I was told this was due to "incompatible differences" between the power supplies (& transformers) between the two devices. They told me that bassists come into their shop all the time with the same problem & symptoms as what I had.
Anyway, have you tried using a ground lift on your DXR10, or via the switch on the AX8? When I switched the ground switch on the AX8 the hum was worse. When I used a physical ground lift adaptor on my XiTone's AC cable - that would eliminate the hum, both at home and at the tech's shop.
This is by far the weirdest, most inexplicable hum issue I've ever come across. Usually it's a bad cable, or bad power. That was not the case for me. It required an additional device (the IC-1) to remedy the problem. I gigged it last night for the 2nd time since I started using the Radial IC-1. My rig was dead quiet. YMMV