There are two distinct trains of thought here, one being the importance of one over the other, and the other, the practical benefits of doing kata. Maybe we can dissect both. Bunkai, when properly understood can open up a whole new world. The problem, as you stated, is having a teacher to point us in the right direction. This coupled with some old fashioned cross training with open many doors. Back with combining kata and sparring, I feel one is sport and the other (kata) is pure SD. Do they intermingle well??
Yes, I agree, and that is one of my pet peeves when I see some people doing kata. Seems like they just move from one thing to the next, without knowing what they're doing. IMO, they're missing a big part of the puzzle.
As for combining both...I do Kenpo. Kenpo has kata. I also spar, however, I tend to stay away from the point type sparring, in favor of continuous, as well as more contact, adding in clinch work, ground work, etc.
I don't think, for me anyways, that it hinders anything I'm doing.