They DO have overall ratings in Madden 12.
What you saw is one PAGE of his traits, not his ratings. Every player has an overall rating, plus a whole bunch of ratings like they have always had (speed, strength, acceleration, pass block, run block, awareness, throw power... etc.)
The screen the OP posted is a new addition. Depending on how confident and consistent a player is, his ratings will change slightly (or drastically) from week to week depending on how he performs (this is used in Franchise mode).
Even within a game, if you get 3 sacks with Dareus (for example) his ratings will actually increase, making it more likely that he will do even better as the game goes on.
It is their attempt to account for momentum. It looks cool, but we'll see.
In any event, overall ratings ARE in the game. Brady and Brees are the 2 highest rated QB at 99 and 98 OVR.
http://www.google.com/imgres?imgurl=http://ps3media.ign.com/ps3/image/article/116/1168111/madden-nfl-12-20110513114254632.jpg&imgrefurl=http://clame.org.mx/madden-nfl-12-screenshots&usg=__4bdwjYxDzjezDUJj6evcTVZTSVw=&h=720&w=1280&sz=404&hl=en&start=24&zoom=1&tbnid=KvRkIM47VHvVlM:&tbnh=110&tbnw=195&ei=iQbxTf_2DsLegQfsofmBAw&prev=/search%3Fq%3Dmadden%2B12%2Bscreenshots%26hl%3Den%26sa%3DX%26biw%3D1024%26bih%3D606%26tbm%3Disch&itbs=1&iact=hc&vpx=323&vpy=317&dur=1052&hovh=168&hovw=300&tx=148&ty=126&page=3&ndsp=12&ved=1t:429,r:5,s:24&biw=1024&bih=606[/img]"]FA system showing some OVR ratings