Hipcentric IS deceiving, and it only gets more challenging as the levels progress. What has surprised me about it (I'm on Level 7, Day 65) is that the lower body section is really a total core workout. I feel the work everywhere from my ribcage to my knees. With each level, there tends to be a slightly different focus (although it is all still total core). I've noticed concentration on the outer hips/thighs, glutes/hams, abs/groin and with Level 7, the inner thighs. Tracy also seems to add more and more balance work and plank work as the levels progress, which of course really works the core.
Tracy does have her own unique style of instruction, which many find difficult. I've always gelled with it, but I think if you're not now, you will get better over time. I found it very helpful to read Tracy's book, which gives more thorough instruction and helps you understand what Tracy is trying to do with her exercises. Tracy says form is very important as is precision and "performance" of the moves, so understanding them is crucial. Perhaps you could try just watching the video a time or two and really focus on what Tracy is doing and the angles. The camera work in Meta is very good. Tracy is shown from a lot of different angles.
Tracy is quite particular on her cardio. She prefers dance and movements that continue her muscular structure work and are varied. She is very anit-repetition with cardio, which is kind of strange considering her muscular structure work is very high rep. Tracy discourages repetitive forms of cardio like running, spinning, etc. I'm not sure about k-bells, as I've never done them, but there are people at our Meta check in (which you are very welcome to join!) who have added in some k-bell stuff. The Meta cardio is very free form. Personally I prefer Tracy's choreographed dance cardio videos. I use them from time to time, and I also sub in some of my other dance workouts. I also use Leslie vids. I'm sure Tracy would frown on Leslie (talk about repetitive cardio!), but I modify it in what I call "TA style." I add in lots of dance moves, higher impact, some of TA's standing ab work and unweighted arm movements. I think TA would be impressed with my Tracy/Leslie blend.
Hope this helps! Good luck!