The cardio issue. Many of the guys on TUF can't afford to train and fight full time and because of this they are not high level UFC caliber athletes. That is to be expected and is really unavoidable. Smaller guys though generally have better cardio which means they don't gas out as easily. That makes the fights look better on TV especially to people who are channel flipping and without a lot of reference points they likely don't realize they are smaller (the UFC uses a smaller cage for TUF).
Also please don't double post, if you want to add something edit it in.
My apoligies but as for 170 and 185 we've seen lots and lots of people gas hard on the show. It happens every season far more than once. It happened this season.
The talent was there for the cruz vs faber division but that's basically because at 125 the ufc can get the pick of the litter for practically nothing at this point.
at 155, 170, 185... its pretty slim pickings. there just cheap slim pickings.