The White Council assaults Dol Guldur?

[Gordis]

I don't think Celebrian or Arwen were on the Council. Celeborn, on the other hand, I think, was there all right.

Also, as I have just read the thread, I noticed a mistake in the first post:

Possibilities not yet closed: Glorfindel, less likely Erestor, Celeborn, Galdor.

Actually rhadagastly proposed Gildor (Inglorion) not Galdor. Galdor, indeed, seems to be a mere envoy of Cirdan, but Gildor was Lord of the Noldor, a Calaquendi Elf, normally dwelling in Rivendell. I think he was on the White Council.

Also thinking of this quote

OF THE RINGS OF POWER AND THE THIRD AGE
But at length the Shadow returned and its power increased; and in that time was first made the Council of the Wise that is called the White Council, and therein were Elrond and Galadriel and Círdan, and other lords of the Eldar, and with them were Mithrandir and Curunír.

I would say that Glorfindel certainly was there, likely Erestor, and maybe a couple more Elf Lords from Rivendell. Glorfindel says:

There are few even in Rivendell that can ride openly against the Nine; but such as there were, Elrond sent out north, west, and south.

I suppose you have to be a Calaquendi Elf to ride against a nazgul. Glorfindel alone took the most probable road, but two more Elf lords were sent north and South. Here are 2 more guys for the White Council.

Actually I think the Council counted numerous members, most of whom followed Saruman over Gandalf. The ones listed in the first post (Galadriel, Elrond, Círdan, Glorfindel) would likely vote for Gandalf, but note: the majority was always for Saruman. I imagine Celeborn usually voting against his spouse. Likely some members were more or less nominal, and didn't attend every meeting. I think Radagast was a member, but not a very active one, preferring his home at Rhosgobel to the talk of politics. Cirdan was likely a rare guest as well, maybe sending a representative instead.

And no Thranduil - nobody called him to the White Council of 2941, he was at home at this time. And Mirkwood had tense relations with "the Wise", especially Noldorin Elves since Oropher's times. Moreover, Thranduil got no Ring to defend his land and must have felt frustrated.