NAT' have nothing to do with Portugese or Spanish airspace so they are pretty irrelevant. There were already huge delays in portugal and nothern spain, due to the NAT tracks being so southerly, something they are not used to, and hence different airways may have been unavailable, and as a result any other rerouting would have added such a significant distance that it may not have been worth their while. Flying above it does not work as you'd have to descend through it at some stage
Better safe than sorry I suppose.