Although I understand I can make my comments better I think the subject of balance is much more complicated and also easier then you describe. And in my opinion, guidelines are more elusive then it looks.
For me each artist is unique, all artworks are unique and both have their own balance. So, as a commenter my own questions are more about the artist and the artwork themselves. And when receiving comment, as my personal experience, the best comments I receive, are not positive or negative based, neither have to be the sandwich, but they are thoughtfull and sincere.
So, a guy saying "Your anatomy is good but take a look on some tutorials about it (link), but good work" for me sounds robotic, cold, and perhaps fake, even with the sandwich... However, a simple "I feel something strange or out of place about your anatomy" is fine, because I wanna know how people really see and feel about my drawings.
Hollow positive comments can be more harmfull then sincere and negative comments.
Encourangement is very important, criticism too, but for a really constructive comment the priority (for me) is the sincerity!
Sorry if I'm being rude, but this is my ideia of balance and I felt I should mention.