The victims were anyone who has held a debt, (mortgage, loan, business loan, etc etc) with Barclays, (and other banks too allegedly), at the time the rates were manipulated. Potentially, someone could have paid more to Barclays than they needed to. Individually, the loss maybe quite small, it would be difficult to calculate. But across the company, those little amounts would add up to a significant amount so as far as claims for damages are concerned, a class action, (or group claim) is more likely.
As for criminal activity, on the face of it, it sounds like fraud, but proving it in court may be difficult, especially with the expensive defense teams the banks would put together, and exactly who would you prosecute. From what I have heard, they can't even agree if Bob Diamond was in charge at the time, or not, then theres all the other managers, traders, etc, so who do you blame.
I'm all for banks being successful and making a big profit which helps the country, but I'm not in favour of customers being lied to, what seems clear is that there is a culture of "anything goes as long as it makes money" in the banks, and there does need to be some ethics brought back into the business. Sadly though, its a reflection of our times, journalists, MPs, cowboy builders, bus drivers demanding excessive bonus's during the Olympics, doctors wanting massive pensions, ........greed is king.