Reread the first four books last summer right around the time ADWD came out, so my memory for details is hazy, but the Lannisters-in-Kings-Landing plotline for ACoK and ASoS as best I can recall was: Tyrion spending the entirety of ACoK fighting Cersei's mistrust of him and greed for power and Joffrey's brutality and stupidity, trying to do smart things to shore up Lannister control and well-intentioned things to protect the people who need it as best he can, but watching as the public credit for his good decisions gets claimed by others while he gets landed with the blame for others' bad decisions. Culminating in Tywin showing up just as Tyrion's effectively won the Battle of Blackwater, and Tyrion waking up from his drugged haze in ASoS to find that Tywin took away all the power Tyrion had consolidated in the previous book and Cersei had been filling Tywin's ears with a very one-sided account of the previous book's events. I don't remember Tyrion as having much of an active plotline in ASoS until we get to the weddings and the murders.

And all of these strike me as still being workable on the show -- Joffrey seems to have more power than I recall him having in the books, and Cersei knows better what he's like but can't control him at all. (Also TV!Cersei seems better grounded in political realities than book!Cersei, which I kind of like but does kind of require that she be more powerless so that the bad decisions that cost the Lannisters are still being made, just not by her.) We've established that she loves her children, very much, so even having a clearer view of what Joffrey really is, I still think she'll be broken when what happens, happens.

The show didn't act like what Joffrey did to Ros and that other whore (whose name I can't recall) was a bit of harmless mischief -- it was a horrifying scene, and I think Dinklage did a good understated job of indicating his regret at having so misjudged Joffrey as to put those women into his hands, even if he wasn't going to make a big deal of it to Cersei.