Yes, the Libor interest-rate rigging scheme should have resulted in more UK prosecutions of individuals who were involved. Rigging interest rates for profit since 2003, big banks made huge profits. When the scandal was uncovered in 2012, the banks faced fines, but only a few individuals faced criminal charges. What the people who participated did was illegal, and more of them should have been prosecuted.
The Libor interest rigging scandal likely involved more people than were charged. Schemes like this are complex, and often involve more people that ultimately end up getting prosecuted. They may have felt there was not enough evidence to prosecute all the people involved and tried to go after the people who were most responsible.
The danger of big money scandals is that those with the largest amounts of money tend to get away scot-free. This is the case in the UK with the Libor interest-rate rigging scandal. Everyone should have been very strictly prosecuted. Examples must be made for the sake of a better, more prosperous nation.
No, more people should not have been prosecuted for the scandal. The people who have been prosecuted are probably serving their time or awaiting trial. This is likely enough. More people do not need to take blame for others. The people who have taken blame are likely the correct ones.