Yeah I read the books before I watched the series. I thought the first season was pretty good but haven't really been into it since then. It is not so much because of the changes but that the characters and the character interaction which is what makes the show interesting are far less so once you know the general plot. I'm not current but if you liked ASoIaF or just good political intrique you should get past your rather trivial gripe and watch the show.
Yeah it is not spoiling to say that those two are uninteresting characters. Sansa in particular is just a bore, Stannis is another rather boring character and it has nothing to do with what role he has in the plot.