I really don't know what s right way to interview, but I do know that you are actually hiring a team not set of individuals. You need to have balanced team (means to be smarter than you on each of the important fronts) to deliver a successful product.

So I guess it might be ok to hire somebody based on brainteaser if you need a sharp, quick thinking person which will be a great asset during brainstorming sessions. I don't know.