Depends on how you would define "wasted". XEL is built to solve computing problems without a predetermined outcome, if that makes sense. Like, you want to find the (short) private key to a known hash. Let's say you forgot your five digits password (you should probably not have a five digit password, but whatever). You can't "compute" this in the sense that the computer gets the question, solves one equasion and has the answer. It has to try different inputs, compute them, compare the result, then try again. In the sense that all inputs will be garbage except one (or probably a few) which is valid, yes, there is a lot of computing power "wasted". But in the sense that this is still the only sensible way we know to solve such questions, no, it is not wasted.