This article does a fantastic job at summarising some of the benefits and reservations of participating in the group class like the one described, BodyAttack. http://coach.nine.com.au/2017/07/06/16/15/bodyattack-les-mills
There a numerous benefits of participating in the group class training, they are motivating, force you to perform at the higher intensity level as you try to keep up with everyone else. Not to mention numerous variety of the group classes on offer that you can pick from to focus on the areas of fitness that are most important to you. You can pick anything from a bootcamp style group training to a spin class.
However, there is one important aspect that not one group class can offer to the participants, and that it is individual approach. Unfortunately, by their design group classes tend to assume that every participant will be able to perform certain movements to some extent, they will offer progression or regression for each exercise. For many people that variation may not be enough, too many of us had past injuries or medical history that can prevent us from performing certain movements correctly. Furthermore, everyone has a different body and for some people certain exercises will be detrimental rather than of any benefit.
Consequently, in many instances before commencing any group class training you need to seek advice from your health professional if that particular group class would be appropriate as a starting point. Hiring an experienced personal trainer can help you ascertain the correct approach and progression to your workout plan. Personal training can be an important tool that can help you learn and better understand your own body.
In my experience, many of my clients had achieved best results through the mix of personal training, group class training and training on their own. Personal training can help you better understand the purpose behind each exercise as well as how to perform exercises correctly. In turn, when you participate in the group class training you will be able to perform all the exercises correctly with minimum supervision provided by the group class instructor, while still enjoying that group class vibe and excitement.