When it comes to more than just simple playback (like slicing, playing random slices etc.pp.) the OT is probably your best bet.
With the latest firmware for the Octatrack you can play one of the 128 static slots directly via MIDI on each track.
Or you can combine multiple of the long samples into a really large sample chain for each track and select from these via MIDI. This way you can have theoretically (64*8 =) 512 samples in direct access. Of course this rules out further slicing …
With slicing and random play of the slices, I guess you’ll need a different approach. Either set up different patterns/parts with different samples on the 8 tracks or just modify the used sample on a track on the fly (change the corresponding static slot to a different sample).
About doing it live - at the same time: what do you exactly mean by “at the same time”? Change all 8 tracks simultaneously to different samples? Doable with different preconfigured patterns/parts. Slice multiple tracks at once? Not possible. Randomize playing the slices on all tracks? Doable with lfos.
IMHO it’s just a matter of specifying exactly what you want to accomplish workflow-wise. At least with the OT there is almost always a way to do it.