There are some patterns offered for sale which don't seem to be drafted by someone who has learnt pattern drafting. Typically these are on sale in small independent outlets who rely on internet fan traffic to build up sales. Not every small company falls into this category though. Beginners are probably better off using one of the bigger company patterns, if only because they come with seam allowances and usually pretty good instructions. Whatever pattern you start with it's a good idea to measure the pieces and compare them with your own measurements to get an idea of their sizing and ease. Some of the guilty fan based companies win sales because they seem to offer a lot of hand holding and sew along camaraderie. A beginner is better off with a decent pattern, good sewing book and access to a site like this where friends will chip in to help.
Some pattern faults which come up are back and front patterns identical in woven, fitted designs, fitted sleeve patterns which have the same curve on the back and front in wovens, crotch curves flattened out (see Morgan's link), too much ease in a sleeve head.
The further you are from the standard measurements the more fitting you can expect to do.