I just set this up today with hardware monitoring turned off. Its an extensive device, and it seems to work well as a standalone interface (8 input channels, etc). Strangest thing though, I installed the optional Line 6 driver that enables you to change the sample rate and it doubled the (apparent) latency. Now, it sounds fine, and it's unnoticeable, which is all that matters, but when I tried to uninstall it (to compare to regular class compliant Core Audio driver), I discovered that the Line 6 driver uninstaller doesn't uninstall this particular driver. You can tell as the Class compliant driver is listed as 'Helix Audio', and the Line 6 driver is listed as 'Helix Lt' (and of course the latency numbers are very different). You have to manually uninstall it, as I found from another (helpful) post:
"The driver will be in Macintosh HD/Library/Extensions. Inside the Extensions folder, you should see an item named "L6Helix.kext." If you don't want to use the Line 6 driver simply remove the file "L6Helix.kext" to the Trash."
​So I'm using the regular core audio drivers now. No immediate perceived difference, but will go back and forth for while as a test. I'm not even sure if the latency numbers Logic give you are accurate when you do this sort of thing. But then again, 20ms is perhaps only noticeable to quick people :D
​The numbers I get are:
Line 6 drivers: Logic X, Software monitoring only. 5 core audio plugins (which should not effect it much); 48kz ; 64 samples buffer. Latency is around 20ms (not too bad). Then: same setup with the line 6 driver uninstalled will show around 10ms (or less). Again, I didn't measure the latency myself somehow, i'm just going by what Logic tells me.
Just a heads up