We probably have rotisserie chicken about once every other month, these days always from Sams. We didn't like the spices in the Costco one, though I've seen multiple online sources claiming the Costco one is better. I've usually found the hot foods at Whole Foods to be disappointing.
Never had one that was underdone, though. I would certainly let Whole Foods know, there could have been an equipment issue.
I usually buy the one that has the darkest skin, figuring it is fully roasted.