"ADAT clock has some issues, in my experience."
I experienced that the analog IOs of a RME HDSPe AIO and a Behringer ADA
8000, synced by ADAT only, can be used together, with THE exception: If
channels should be in sync, e.g. a right and left channel, than those
right and left channels must be from the RME or the ADA 8000 only, a mix
of both does result in unclean phases.
However, the OP doesn't have this issue.