I have to say in this part of the world, ie. the Middle East, "WILCO", is pretty useless and we need a readback of pretty much all instructions. Partly due to the Russians and related cousins from the various "-STANS" who try to understand instructions but invariably don't, but will respond with "WILCO" anyway, or the American military guys who when they aren't sure of where to go, will reply "WILCO" and then go where they were going before regardless.
So it may clog up the R/T but it is still the better way to go.
Still don't agree with the descend and maintain instruction, and will try not to use it in the future.