Job action combos one button

[Absurdity]

"Single button" does not necessarily encapsulate "single action".
Healers are both.
PvP combos, Gnashing Fang, Continuation, and the like, are only the first.

That does however require SE to actually add new actions/combos when they consolidate our 1-2-3 into a single button, something that is absolutely not guaranteed.