I have same issue. No Audiobus 2.1 function with ios8. This issue is also on the iSEM app as well. Please if anyone has info on status of ios8 update for Audiobus functionality, please let us know. I have emailed Arturia support 3 days ago and still no response.
I just got this from Arturia Tech support:
"Hi Andrew,
For the iSem, a new update should be released in less than 2 months; it will ensure iOS8 and Audio Bus compatibility.
Concerning the iMini, an update should come before the end of the year.
Best regards,
Jerome
--
Technical Support inquiry
technical-inquiry@arturia.com"
So looks like we will have to wait a couple months for this.