As a die-hard fanboy of Arthas and the Lich King, I'm deeply disappointed. First, Bolvar is presented as a weak husk that cannot be compared to Arthas. Peak Arthas would simply cut Sylvanas in half or freeze her before she would even come close to him.
Second thing - the build up. The Lich King entity, tied to Ner'zhul, was very mysterious. We know that Ner'zhul tried to merge with Arthas and Arthas didn't allow him to, but his soul was still present inside the helmet. When Bolvar took up the helmet, we didn't know anything about what's going on inside of his head. What about Ner'zhul? Did the fallen shaman merge with Bolvar? Did he corrupt Bolvar? Did Bolvar banish him just as Arthas did?
All that could be, could have been, was torn apart just like Helm of Domination. All that build up leads to nothing... but does it?
On the panel, Ion said that in Shadowlands, we're going to experience the world as it is without the Lich King. But okay, Terenas said that there must always be a Lich King. That didn't really make sense in the literal meaning of these words, but we had multiple theories - did Lich King corrupt these spirits just to survive? Did he want to manipulate us so he would stay alive, inside a new host?
It turns out that Terenas was for real, but apparently 'restless scourge' was retconned and now it's about the barrier between two worlds. Without the Lich King, the barrier apparently falls, but... why? Like, wasn't Lich King an orc shaman that was destined to prepare Azeroth for Burning Legion invasion using his death magic? Ner'zhul didn't keep any barrier intact, neither did Arthas. And what about time before the Lich King? Before Kil'Jaeden trusted Ner'zhul inside an icy prison to Azeroth? There was never a Lich King until that.
If my boy Arthas was still alive, he would cut that banshee bitch in half without any ceremonials.