[Terenas] Karazhan - Where are your upgrades from

[Kevin]

Chess Event is not optional if you want to get to Prince, and Shade of Aran is.
It is highly recommended that you kill Aran, as not only does he control ~60% of the trash in the path between Curator and Prince (~35% Netherspite 5% Illhoof), but you can teleport to his room from the doorman, which helps a great deal with time. You also have to kill Aran as part of the chain to summon/kill Nightbane.

I've also updated my list.

It's my understanding you can just walk through the Chess room and head on to prince you don't have to play the game. It doesn't control any doors or gates as I understand it. The definition of what was optional is a bit arbitrary anyway and I'm not sure why I have Nightbane listed as optional since he used to be needed for attunements and for the reasons you stated Aran isn't optional either because of the trash he controls and being needed for the quest chain.

At this stage in our progression and with the attunement changes the designation of optional is completely meaningless anyway.