Gove isn't scrapping it because of workload....
The curriculum time it takes is perhaps one issue though....
For me, the conflict of interest teachers have has to be a huge issue with the way pressure is being applied to them to gain results results results (end of)
I'm pretty sure also that too often (however you design it) it tests literacy skills more than the subject skills its designed to test. Now, communicating your subject skills is of importance, but if it is a barrier to a student showing their true ability, then the voracity of it must be questioned.
I know that you are right to point out that execution doesn't mean it's a bad idea, but when so little coursework actually works, I would suggest that it's almost possible to do properly.
However, patently, art, wood work etc have to be largely assessed this way, but they are more the exception.
Politicians certainly should stay out of it. Too much chopping and changing with party systems is very disruptive for kids.