No problem as stated.
We just did an upgrade from 6.6.2 to 6.8.4.
6.6.2 Cummulative patch 10
6.8.0 prep patch
6.8.0 upgade
6.8.0 RPM rollback patch
6.8.0 Cummulative patch 4
However we did hit a bug causing us to not be able to edit our captive portals and you need lms to do license **bleep** which they failed to do for us even though we opened a ticket weeks ago for it. Very disappointed in Aruba there but upgrade wise, it worked pretty well.