I've already turned off the "press and hold" setting via the Terminal, with defaults write -g ApplePressAndHoldEnabled -bool false, and restarted. But the macro still only does one forward delete at a time.
Now, does anyone know why this sort of control flow is necessary on the new Macs? (for my problem, Chris' problems and no doubt many others) The macro on my old machine is the simple one-step shown above, and works perfectly.
I suspect that's because of the press and hold setting which I mentioned in my original post. It's to help people enter accented characters, so if you don't need that you can turn it off. Even if you do need it, there's a moderately easy way to achieve it via option and a small subset of keys. (I can list them if you need them)