I suggest reading this article by Dennis Fink, it is very enlightening as to the 'purpose' of kata. In my training, I've been told, that in the old days, Okinawan Karate practitioners never used to have the basics. They only had kata and bunkai. As you advanced further through the grades, you would learn more complicated kata, and more complicated bunkai, at the rate that you can absorb the information. Kata and Bunkai go hand in hand. Kata without Bunkai is like dancing. In my opinion, practicing bits of kata in combinations and the appropriate bunkai enough times should make you do an effective counter to someone's attack. In my Isshin-Ryu training, I've now done Seisan enough times to employ the moves in that kata in a real fight.