While collimation is important, it is typically way overstressed in threads like this. Yes, actual poor collimation will limit the level of detail, and make it difficult to get decent focus, but seeing is far more frequently a much larger factor. Collimation won't matter much at all if the seeing is poor...which is the norm for many of us. Collimation can be fair and still give decent detail, it just won't provide that last bit of crispness that precise collimation provides. You can tell when the seeing is good if the collimation is holding you back. I have seen the trade off in collimation and seeing issues with SCT, MCT, Dob, and refractors (yes, even refractors are prone to collimation/alignment issues at times.)
If collimation is the source of the problem, then it should be apparent in the image as well. Turning to a bright star and racking focus back and forth will confirm if it is a collimation problem.
This thread started two months ago when Jupiter was lower in the morning sky, and it was likely very poorly placed for most observers. Therefore, the seeing aspect is even greater, because seeing problems are often amplified many fold at low declinations. And the thread was posted mid winter, when the seeing is typically at its worst.
~250x from an 8" Dob isn't asking all that much if the seeing is good and the planet is well enough placed in the sky. My old 8" SCT without any fans does well at 300x in good seeing. (I won't claim its collimation was historically "perfect", but after some initial fine tuning it held for well over a decade with virtually no tweaks.) From what I have seen of Jupiter through our 10" Dob I would expect an 8" Dob to be good for somewhat over 300x if the optics are good and conditions support it. I would expect it to have somewhat of an edge in planetary mag/inch compared to an SCT from what I have seen.