I can give a definition of sloughing off: Surviving on other people's money when you're capable of generating your own to survive off of. This especially refers to the essentials like food, shelter and clothing. There are special exceptions to this definition, but qualification can solve this. I happen to believe this is most people's definition in the context of welfare discussions. I think very few people believe anyone is getting rich off welfare, so I don't think getting rich off of other people's money is in danger of becoming the common definition of sloughing off. I don't know of a single person who believes welfare recipients are buying houses and good cars off of welfare benefits.
I am unsure what you mean by 'greatest benefit to those who need it'. Strictly speaking there is no overlap causing an issue between 'those who need it' and avoiding 'undeserving people gaining from it'. If you're supplying it only to those who need it, then you're not supplying it to the 'undeserving'. So, what I think you mean is whether I think A) everyone who needs it gets it, but we also end up supplying the undeserving, or B) no one undeserving gets it, but then some who really do need it go without. There is no perfect system, so I would agree these are our choices. And I would choose A every time.
But that wasn't what I was addressing. PK claimed no one was sloughing off, and I correctly challenged that statement. Like I said, I like to be honest, and honesty is that some people are sloughing off. It doesn't mean I think we should do away with welfare. I accept there will be this problem. Now, what is the reason I like to be honest? Because you don't even attempt to solve problems you don't think exist. Maybe there is a way we haven't thought of yet to weed out the sloughers without denying care to those who need it. Maybe there is a way to improve the situation. But, you never seek to improve if you indulge in blind spots.
So, I shine light where I think it needs shining.