I'm trying to set up a WA for the Mythic Dimensius fight that triggers once per set of adds - basically, once an add reaches 1 HP on each set, it starts to cast a full heal, and I'd like to show that cast bar - but only for the first add that triggers it per set (I don't want the cast bar restarting when subsequent adds hit 1 HP, and I don't want to see multiple bars - just that first bar, showing the one important instance of the cast).
I thought of using the Count option within some trigger types, but I'm not positive how many times the cast might trigger per set. It might be possible (first add set is 6 adds and subsequent are 4 adds, so perhaps I could trigger on 1, 6, 10, 14), but I'm not sure if that'll work.
Is there a better way only allow the first instance of a trigger to be recognized until that trigger has expired completely?