I recently asked Lax how one would go about making a "Reverse Round Robin".
As in, press the key in sequence and have the same character target the party in succession.
As always, he had a simple solution to the task at hand.

Take your FTL Target Me mapped key.
Copy it to the clipboard.

Paste it somewhere, so you now have a copy.
I have started to make a Keymap for each individual team, which is only loaded for that specific team (to make organizing nine distinct character sets less of a nightmare), so I pasted the Mapped Key in that Keymap.

I renamed the Mapped Key, "Healer Target Me".
I have removed the hotkey for the mapped key, as I want my hotkey to do the normal FTL Target Me still.
Also changed the target of the mapped key, to just the Healer character.

I then made a new Mapped Key, which I have called RR Shield.
I assigned a hotkey for this mapped key.
Under advanced, I have the box checked reset to Step 1, after 15 seconds from first press.
I've given this six steps; I have five toons on my team.

Step 1 Does:
Do Mapped Key Action >> Keymap: 4xDK/Healer Team >> Mapped Key: Healer Target Me >> Target: DK 1.
Send Keybind >> Target: Healer Character >> My wow keybind for PW: Shield
I have checked, do not advance to next step for 1.3 seconds (1 second for the GCD, 0.3 seconds to account for latency).

Step 2 Does:
Do Mapped Key Action >> Keymap: 4xDK/Healer Team >> Mapped Key: Healer Target Me >> Target: DK 2.
Send Keybind >> Target: Healer Character >> My wow keybind for PW: Shield
I have checked, do not advance to next step for 1.3 seconds (1 second for the GCD, 0.3 seconds to account for latency).

Step 3 Does:
Do Mapped Key Action >> Keymap: 4xDK/Healer Team >> Mapped Key: Healer Target Me >> Target: DK 3.
Send Keybind >> Target: Healer Character >> My wow keybind for PW: Shield
I have checked, do not advance to next step for 1.3 seconds (1 second for the GCD, 0.3 seconds to account for latency).

Step 4 Does:
Do Mapped Key Action >> Keymap: 4xDK/Healer Team >> Mapped Key: Healer Target Me >> Target: DK 4.
Send Keybind >> Target: Healer Character >> My wow keybind for PW: Shield
I have checked, do not advance to next step for 1.3 seconds (1 second for the GCD, 0.3 seconds to account for latency).

Step 5 Does:
Do Mapped Key Action >> Keymap: 4xDK/Healer Team >> Mapped Key: Healer Target Me >> Target: Healer
Send Keybind >> Target: Healer Character >> My wow keybind for PW: Shield
I have checked, do not advance to next step for 1.3 seconds (1 second for the GCD, 0.3 seconds to account for latency).

Step 6:
No Actions.
But have checked, do not advance to the next step for 300.0 seconds.



Adjust the Do Not Advance, for each of the Steps with an actual cast, to account for your latency and the GCD.
Adjust the reset to Step 1, to determine how often the sequence can fire off.
And have Step 6 long enough, that it won't loop back to Step 1 until the mapped key resets.

Then decide if you want to manually push the key, or to include it as a Do Mapped Key action, as part of something else you are already spamming.