It's what you make of the job of course, but I don't agree at all that it's only those who have done something wrong who ever get a 'hard time'. I'd agree with you that there's a 'cushiness' scale and the average backbencher tends to have the best of it, but the abuse MPs get on an almost daily basis isn't something I would be prepared to tolerate for that money. Admittedly a lot of it is just random trolling or in more sympathetic cases perhaps, those with mental health issues, but that doesn't mean it's an easy job and a lot of the daily grind they do is thankless.
You also have to factor in the fact you basically don't get a weekend for 5 years, especially if you're a Minister. Monday-Thursday you're in Parliament and Friday-Sunday, plus all recess breaks, you're in your constituency.
Unfortunately the minority of lazy/corrupt/self serving MPs, along with the rise in aggressive political commentary, means that the whole profession is tarnished in public eyes. A lot of MPs work very hard for fairly little return though, and that should be acknowledged in my view. For every Brooks Newmark, there's another 600 odd MPs out there dutifully fixing Mrs Blogg's bin collection issues without scandal.