Send a Shinobi out and keep them concealed as long as possible until they can see the EMP Pulse Relay. Then use snipers to destroy the relay. Others things you can do is control an enemy mech and send them searching. I got lucky and controlled a Sectopod. Has to be something that can endure enemy fire or hide from them. You may have to send troops our slightly to back up the Shinobi if they gets in trouble. Give your Speiclaists Skulljacks for the hacking bonus

Well, the same thing happened to me. Its unwinnable unless you get to a previous save, get back all your best soldiers and prepare for the worst. With 12 good soldiers advent is defeatable. I agree that the avenger attack has slightly too much opposition.

I don't have the choice of the team, I don't have a shinobi available at the moment. I can't delay... I've one sniper for the mission. I don't like the idea of loosing on something impossible to avoid... It's ruining my campaign...

It's just my opinion, but I think this needs to be modified. I won't play the mod until I'll have to fear this "wall". I don't wan't to ruin a long campaign on one impossible/unavoidable event.

There are more surprises like this in LW2. If you dont have a savegame or played on ironman, those surprises will ruin your campaign. In the future I know now that when the UFO hunt event is up, I will be prepared, just as when I failed to do a mission leading to a retaliation. And I guess I will find many more such traps.

Avenger defense is pretty overtuned at the moment. Its something you have to be prepared for at all times, which is why having a 60+ roster is so important in long war, so that you always have a decent squad in reserve

I've more than enough soldiers for the mission, but I don't keep my "A Team" at home just for that.
And it's the fact of being bloqued by this mission that I find annoying. I just can't skip... I don't remember LW1 having blocking missions... and this one is really more difficult than the rest of the game...