I am currently offtanking for one of our guild's kara groups. Our group seems to be stalled out a little. We can consistently down all bosses but Prince, Nightbane, and Netherspite.
This week was our first shot at Prince and on one try we had him to 9%. So close! A lot of our trouble was getting used to the event and bad luck with the infernal drops.
We are progressing as a group because of individual improvements and better knowledge/experience. This leads me to believe that we will eventually master the castle.
Also, we are mixing up our groups. The other raid group is a little more advanced and better geared. Interchanging a few players will balance out the two groups and help our overall progress.