It is my understanding that the asymmetrical-thrust crosswind technique is useful for reducing the amount of rudder required to keep the longitudinal axis aligned with the runway. (You still need to bank to correct for any drift.) If you have the rudder effectiveness available, I don't see how using this technique is practically useful (unless, of course, you're landing in a situation where the rudder is not able to keep the aircraft aligned, but if that were true I bet the bank required to correct for drift would be dangerously excessive). Either with asymmetrical-thrust or the forward-slip, you're still slipping the aircraft. Assuming this, then, why is it even considered as pragmatically useful?