Im trying to complete Castle Nathria on the LFR option and I’ve got to the Stone Legion Generals but I cant seem to figure out how to get the 2nd of the two bosses to activate. Does anyone have any links to a good set of tips on how to solo the fight?
SOLUTION: I figured it out, finally, but thanks to those who offered advice.
During the transition phase you need to collect the red orbs and take them to the NPC. When his bar fills, it will break the shields and make the bosses swap. Do second phase like you did first, then another transition phase begins. repeat the red orbs gathering, so you can face both bosses together in last phase.
Thanks for the response. I did eventually find that out. I managed to do the orb thing and kill both bosses. However after the fight, the two NPCs just stood around and didnt open the door.
Not sure if there was something I was supposed to do.
I thought perhaps the Denathrius fight was a single choice LFR. I guess I need to go back and check tht. (Edit: turns out thats true)
On LFR? Denathrius is his own wing, isn’t he?
Yes, I found that out. Problem with the list of wings that the NPC offers, they have these confusing names - which might have meant something back in Legion but mean zero to me. I had no idea from the description on the list which one contained which bosses. It was only by guesswork that I figured it out finally.
The wowhead overviews for raids tend to have the wing names/bosses delineated.
Thanks for that. I still think the weird names in the LFR npc’s list is a rather dumb idea, and that I shouldnt have to go outside to a site to figure out what they mean. I mean, why not just called the final wing:
“Denathrius”
That would make it absolutely clear. 
When it’s current, hovering over the drop down will tell you which bosses are in there, and whether or not you’re saved to them.
Be good if it worked on Legion LFR… which is what Im doing atm.
It’s applied to all LFRs you can queue for through the queue window (which in practice means only while it’s expansion is current).