I am trying to simulate the different BRF boss fights and I am running into an issue on Hanz&Franz and Iron Maidens where one boss leaves for a period of time.

I was going to do something along the following:
raid_events+=/adds,count=1,cooldown=90,duration=20

for H&F but I believe it will cause the add to have an execute phase for the last 4 seconds of each cleave phase which is not very representative of the fight.

The same issue would be had on Iron Maidens when one of the bosses goes to the boat.

Does anyone know how to either negate the execute phase on the add that spawns, or make a raid event where the off-target becomes invulnerable (though I would like dots not to be removed)? As I understand from the SimC site, the invulnerable command only applies to the current target, there is no target switching possible, and it removes all dots so I don't think this would quite work out.

Can I make the boss become invulnerable in its APL (if I make a custom enemy)?

Thanks for any ideas!