I personally don't care for the 3-2-1 formula she uses, I tried another from another instructor that also used it and felt similar (The other instructor was Chris Freytag and I think it was lower impact than 30DS so you might like it better--I don't recall the name of the workout as I sold it and 30DS). I don't like the one minute of ab work as my heart rate recovered too much so I don't feel I get good enough aerobic benefit from these workouts, and the strength is often a little light--more endurance oriented so it was limited there too.
But if you like it, you might find you also like creating your own workouts that fit this structure. There are plenty of options for smart phone interval timers or online timers and if you find one that allows for three intervals it is easy to do. Set one for 3, one for 2, and the other for 1. Or just set it for two intervals and do core work at the end (I prefer that). You could get ideas for the exercises from Spark or from another site like Bodyrock.tv. I think it was 3 minutes strength, 2 minutes cardio and one minute abs (or do I have the strength and cardio reversed as it has been years since I did these).
Another option, there are a lot of workouts that alternate between strength and cardio but don't use the 3-2-1 formula. One that comes to mind are the Jari Love "Get Ripped 1000" and Getted Extremely Ripped 1000" and all the 1000's (I have only tried those two). I don't know if there are any that are 30 minutes but she has premix options. I always just did the entrire workout which was an hour, but the premixes may divide it into shorter workouts. They alternate between cardio and strength and have a low impact option for the cardio (involving a step). I used them last holiday season to help with damage control from Thanksgiving, Christmas, New Years and didn't gain any weight despite holiday eating and not tracking food intake (I don't recommend this though) so I think their calorie burn is pretty good (though not the "up to 1000 calories" it boasts, well probably someone would burn 1000 calories doing these it depends on the person's size, etc).
But generally I prefer to do cardio workouts and separate strength workouts and just do fewer of each (like alternate days, 3 cardio and 3 strength). I think that is more effective for me in terms of actually improving both strength and aerobic fitness. But the best exercise is whatever you are motivated to do!