All very good in theory, but you'd have a hard job proving liability or negligence. The fact is, performed correctly, the swerve is perfectly safe and reasonably straight forward. My students (once over their fears) haven't struggled with it at all. During training you say you couldn't reach the required speed - how big is the training area you are using? My pad is 20m short of the DSA test centre and we don't struggle with the speed.
Ultimately, all crashes are the fault of the candidate, if you look where you are going and STAY OFF THE FRONT BRAKE, then you will make the manoeuvre. The problems I have witnessed are that students tend to look down at the speedo as they are crossing the speed trap, look up, see cones, panic and brake, with the inevitable result.
Therefore there is no negligence on the part of the DSA. What I would be interested to see, however, is the DSA risk assessment for the test and what that highlights.
I'd like to also point out that I am an ATB, not a DSA employee. I am not at all happy with the new test, I think it's largely pointless and yes, I do believe the swerve is unnecessarily hazardous because a novice reaction is as I've detailed above. It takes a lot of experience and/or training to counter that instinctive reaction. I do think that the test is here to stay, it will not be revised in the near future, because that would be an admission of fault on the part of the DSA, so we have all got to make the best of it. Unfortunately, people will get injured and bikes will get damaged in the process.