I don't think our current system is optimal (again, statistically very unlikely that we just so happen to have the best system possible), but I think it's much closer to optimal than one at the very end of the spectrum.
And I actually agree with the general sentiment, that we've gone too far towards policing benefits. I think we probably spend too much on tackling benefit fraud; I doubt it makes sense from a cost-benefit perspective. How much do we spend on tackling fraud vs how much do we save (including deterrent effects)? The general goal that we could save money by simplifying our tax/benefit system is well worth pursuing.
But I think the starting point for that should be to focus on changing what we have now. Iain Duncan-Smith had the right idea, IMO: bundle benefits that are triggered by the same or similar means-tests together and pay them out as one single benefit. Aside from anything, imagine the upheaval for some families, who were used to receiving £13,000 in welfare benefits and have budgeted their whole lives around that number, but now have to deal with only £12,000? A £1,000 cut might not sound like much, but it could be the difference between survival and bankruptcy for some people. People have been protesting over far less.
It's a shame that benefits have now become seen as something which in-work people pay to a group of out-of-work people as a kind of charity. That's not how they were designed; it's supposed to be a kind of collective hardship fund, where people pay into it while they're in work so that they can benefit from it when they're not. The people paying into benefits and the people receiving them are fundamentally cut from the same cloth, and I think we've lost sight of that. It's an unfortunate side-effect of the Thatcherite mythos. On one level, it can only be helpful for people to believe that with enough hard work they can be wealthy enough to live comfortably, and that with a bit of talent, hard work and good luck they can be whatever they want. However, the side-effect of it is that it others those who don't succeed: the corollary to 'anyone can succeed if they work at it' is 'anybody who fails to succeed didn't try hard enough and still isn't trying'. That's still something which people believe, even if unconsciously.