When testing Feral macros, I've had my toons (anywhere from 3-5 of the team) run around the target dummy.
That is with an IWT / DPS spam speed of 2 clicks per second.

Have not had the toons run off for the sunset.
But have had them go for a different target dummy then the one I was targeting.

For PvE, its pretty easy to have a toggle which enables/disables the IWT.
Click the DPS move with IWT enabled, and then hit the toggle to disable the IWT.
While continuing to spam the DPS move.

For PvP, with targets who are constantly mobile...
We pretty much need to leave IWT enabled the whole time.