I should probably add as well... this could also be a 'limitation' of the internal routings of the USB buss of the MacBook Pro?
But I find that hard to swallow if i'm running things that take up a lot more bandwidth on the same device just fine.
Yeah I know there is a continual feed on this subject lol, but just thought i'd post my findings with the Overdub 
Thought I'd mention to people that might be interested...
I just got an Elektron Overhub because i'm running a few things off my MacBook Pro 2.3Ghz 15 Retina i7 (11,3).
Sad to report that having nothing plugged in to any USB ports, except for the Overhub and Virus TI2 Polar into the Overhub doesn't work. It states 'MIDI driver failed - The MIDI driver failed to start or is not installed. This can happen if you have connected too many USB devices. Also try to install the Virus TI Software again.'
I tried this both with the included Elektron USB3 cable and a USB2 mini cable to see if that made any difference, it didn't. As well as obviously doing the full reboot of the Virus, DAW and computer in between to be absolutely certain.
However the Overhub works great with an Apogee Duet 2, MOTU XT, ilok, Analog 4 and Minitaur all plugged in together. And then having the Virus in the second dedicate port of the MBP.
Really love the Virus TI but it's still going to be that titchy moody synth with this stuff 
