A group of us did Feds from Farmhouse creek / Moss Ridge late last year (19-23 December, ie. 5 days).
We ran into a party of 6 on their return from the EA traverse near Cracroft (day 1).
We ran into 1 solo walker on Moss Ridge (day 2) who ended up joining our party for the duration of the trip + saw another couple at Bechervaise (day 2), tho they moved on along the Eastern Arthurs traverse the next day. The only other party we saw was a group of 2 as we were nearly back at Farmhouse Creek (day 5).
As we went before the Xmas-NY period it was probably a lot quiter, i'd expect there to be more parties than this during that period as (nearly) everyone has holidays then, particularly after Xmas.
If you can I'd suggest going in a couple of days before Xmas to beat the crowds.
Good luck, it's amazing country down there