Mixing two cabs with different driver configurations (such as a 4x10 and a 2x12) often yields results which are less than what you'd get from either cab, alone, as the sound waves emanating from each cab can interact with each other in less than ideal ways. However, sometimes, the mix and match works out well. I tried a bunch of different combinations of GK cabs, and I had expected that the 412 or two 2x12's would be my favorite. However, when I did this, I actually preferred the 4x10 with the 2x12. I have since gigged this mixed-cab combo, and it has performed well on the job. That being said, I can typically get by with either one Neo410 or one Neo212-II. I really like the Neo212-II with a single Neo112-II on top, too (which is also something normally frowned upon).
As always, though, YMMV.