I use a double tap macro like the above. I actually have three of them (One is self-heal, one is a mouseover macro for Clique to heal an ally, the last is to res an ally). If you're wondering why on the last two, it's because I'm usually a bear.
I've heard that you can get it down to one button by disabling the ability to unshift automatically when trying to cast a spell:
Code:
/console set autounshift 0
I haven't tried this though, and from what I've heard (again haven't tried, and I'm stuck at "Connecting" right now)
Code:
/console set autounshift 0
/cast Nature's Swiftness
/cast Healing Touch
/console set autounshift 1
does not work.