All you have to do is shock the taunters and they waste the ability its its a pseudo buff immunity, in fact with TFPs buff immunity move you really shouldn't even have to attack them for stun or ability block. I'd recommend you ability block Leia though to prevent her invisibility if she doesnt get buff immunity.
A lot of the event depends on RNG so you'll have to play it as it comes to you. You are also correct about the tm reduction immunity, so that's why Palps is considered the better leader, for the max health, potency, tm gain, and heal on palps/ vader.
That being said I want to reiterate that this event will be very easy for you as when I did it i had g8 palps, tarkin, and storm, g7 magma, and g9 TFP. The fact you are way geared over that and have Vader will make this super easy for you.
Side note to anyone reading I would not recommend trying to beat the event with the squad I used, it took me 6 hours of continous play to get the right RNG to beat it.