With Tirion dead, who even knows of Bolvar outside of the DK order?
He is a nice guy, he gave me swords, dragons, pets, cool spells and much more.Maybe if you get to know him better and...join the Ebon blade you will see that he is cool person.
Sylvanas (confirmed in Edge of Night short story) and Tirion, it seems that other faction leaders also know. During the fire mage artifact quest, Modera and Aethas indicate they know of the Lich King. It's usually the general public and soldiers that have no knowledge of him.
However, these are the people that know of the existance of the new Lich King. Many of them do not know that the new Lich King is active and behind the Ebon Blade's actions.
It was always supposed to be Darion. Tirion was never in the files as a follower during beta, Darion was.
The entire attack on Light's Hope was a test of Darion's loyalties, because he's opposed to it. His self-sacrifice was a necessary part of the ritual to create the Four Horsemen and bind them together. Everything happened according to Bolvar's keikaku.
In that quest you can choose how you approach it. I managed to not pull anymobs. So in my "view" of the quest I didnt cause the reds any issues.
Only the paladins got wrecked up. One mage might have an idea about the LK but thats it. So far as everyone outside of the Ebon blade knows the LK died with Arthas.
Some leaders will know by now (as indicated by some NPCS). But he's still low on the radar thanks to the legion.