I think the biggest mistake is to consider the OT as DAW replacement. The term “performance sampler” is great because it highlights that the OT should be viewed as an instrument, not a workstation. Sure, it is a very versatile instrument, that can be used as a sampler, granular synth, loop machine, live hub, mixer, midi sequencer, effects machine, audio morpher and many more. But there are still things that the poor time stretch, the limited number of tracks and effects make the octatrack bad at doing. And for these, having a DAW around will make your life much much easier, and your time with the OT way more fun.
Recently i worked on a Dub like live setup with 8 tracks playing loops and stems, and the OT acting as a mixer + effects, and I would never have even tried that if I had to prepare the stems and loops using the OT itself. All the preparation has been done in Ableton, the stems are set to the correct BPM, level and pre-mixed in there and then are exported to the Octatrack to be performed, which it does very well!
Even sample editing (and particularly sample chains creation) is easier done in dedicated software than in the OT. But once they’re edited, it becomes so fun to manipulate them inside the OT.
One key aspect of the OT is to know what you will enjoy doing with it, and what you should better use something else for.