target-of-target (or <tt>) should handle dps skills while healing--as long as your target is targetting something. i've exclusively set all of my healing dps skills to macro for just that (since macro action limitations matter absolutely none on a class that only presses 3 offensive buttons ever) since i play on controller and trying to change targets from party to enemies and back again on the dpad is a brand of suffering i wouldnt inflict on my worst enemy.
they usually look something like
"/merror
SKILL <t>
SKILL <tt>"
so that i can still manually target stuff with them when need be if i'm doing the slog that is healer questing, story or overworld content for whatever reason