Hello,
I was soloing ToS to complete the Legionfall campaign since I can’t LFR for it, and I tried several times to complete the Desolate Host encounter, but whatever I tried, whatever order I killed them in… the woman and the engine dies, and the desolate host disappears… not sure if related, but also when it spawns it just stands there - doesn’t attack me.
The same thing happened to me. I doubt Blizzard will ever fix it. They don’t care about older content or how we feel about it as players. That’s why they always lose subs.
Hate to necro an old post or whatever, but I had this issue too and this was the only post that came up when I searched for the issue;
I’m pretty sure you have to be in the spirit realm (the one with the Soul Queen) in order to aggro the Host: if you’re fighting the Engine then the Host is unable to attack you and will despawn immediately after you kill the Engine.
Hope it’s not too late to help!