The countersong ability seems quite out of place for the archivist bard - it's strange that they didn't replace it. Does anyone have a suggestion as to what a suitable replacement might be, that fits better with the archivist concept?
What better way to make sure nobody interrupts your work in the library than to shut down that sort of magic?
Well, okay, but countersinging doesn't seem like the right solution. So maybe some sort of silence effect?
Well remember, it can be ANY Perform check.
Perform: Oratory might very well be in character for an archivist. You could play it up as him reading his notes out loud or something, doing that thing where he excitedly latches onto a subject he's passionate about and just bowls over anyone else trying to speak or do anything.
Countersong is actually restricted to Perform (keyboard, percussion, wind, string, or sing). That's one of the reasons it didn't seem appropriate for archivists to me. But maybe the easiest fix would be to just extend that to oratory for archivists.
Just talk sing.