we have 6/cadaver. typically, though, 3 dissect for each lab, with one person from the 1st group of 3 presenting to the 2nd group of 3 prior to their dissection. this works out well, in my opinion.
and as much as i complain sometimes about anatomy lab being a waste of study time (and i DO complain!), when it comes down to it, the labs and features i know the best are the ones where i dissected - where i had to dig around, find points of reference and trace nerves or origins, etc. and the ones i know VERY best are the ones i had to present for the dissection i did. i.e. i have to find all those wee structures on the list, show them to the rest of the group and relate them to other anatomical landmarks. i may complain (because it IS a lot of time, and often, i really don't want to be there) but the labs that i actually participate in are the ones i know the best.
we have an obese cadaver, as well (and that slows you down a bit), but learned within the first two labs how to efficiently clean so that we can find the structures quickly. we've got a couple very good dissectors in our group, too, along with a person or two who are killer with random memorization of landmark relationships, which helps a lot. and once you get internal, the excess fat is less of an issue.