Why Johnny Can't Brand

If we can define the unique qualities of a product through it's brand is it more important to have a unique product or a good brand? There are times that I feel that I've been duped into buying a bad product by it's advertizing. One of the rules for a top brand was said to be that your product must deliver in the specialty that's being claimed, so I wonder if this element of branding becomes a distraction from what costumers really want. When I buy a highlighter that says “No Smear” on the side and then after I've bought it I find out that it's true to it's claim but it also doesn't highlight very well, I wonder at what point the company lost track. I think that we've know for a while how to make a good highlighter, so is this method towards branding degrading the products that we buy?
It makes good sense in my mind to maintain a DSI when branding a product but maybe I would add a rule to the list: Does your unique position affect the integrity of the product you're trying to sell? If it does in a negative way then it's time to reanalyze either your product or your position. I don't feel that it's necessary to trick people into buying a product or specializing in solutions that create new problems.