More work = more violence? That seems neither intuitive nor counterintuitive to me. There is a reason that we refer to certain shootings as "going postal" rather than "going unemployed." Lots of people hate their jobs.

I would assert that a welfare state that functions well (by "well" I mean that it efficiently churns out the welfare benefits) stands a good chance of experiencing very little violence because people are getting a large part of their income for little more than filling out paperwork and demonstrating need and/or helplessness, real or faked.

I would also assert that a relatively wealthy society with a non-existent welfare apparatus could quite easily turn violent if a large portion of the population is poor (low income and/or few assets) because the sense of inequality and rejection, merited or not, will rile people up or make them prone to being riled up by agitators.

I think there are a lot of other factors besides income. Are people upset? Do they blame the gov't? Do they feel threatened (by an ethnic group gaining power, an ideology gaining power, laws changing significantly, etc)? You can have a high-paying job, be angry about something unrelated to income/assets, and blame the gov't. Consider how many rich comfortable people hate(d) GW Bush and were willing to cough up cash to defeat him and, when that failed in '04, were willing to cough up cash to defeat McCain simply because he was successfully portrayed as Bush II. Grievances can come from anywhere. While they are often real or legitimate, they need not be.