Dog licences would make no difference because the irresponsible owners wouldn't get a licence in the same way that irresponsible owners don't get their dogs microchipped.
No one polices the microchip law so what makes you think anyone would police a licencing law?
Walking 7 or 8 dogs, as this woman was, meant that she had absolutely no control over the dogs. Having them on leads would have made no difference. If 7 dogs on leads decide to pull away from the walker there is absolutely nothing the walker could do to stop them and they could still turn and attack the walker.
There is a law in place that everyone walking a dog must be in control of it. Clearly this woman could not have had control over these dogs, but again no one was around to police the fact that she was walking dogs that she wasn't in control of.
There's no point in bringing in laws that no one is going to enforce.
There needs to be more, tougher, laws brought in with regard to breeding and selling dogs, and those laws need to be enforced; unfortunately that won't happen.