The game has finally come to the point this league where Currency Tab has useless slots

Though seriously, stacked decks. I used to dedicate an entire premium tab to just selling those, before I bought a second currency tab for trading currency.

I noticed the same this league.

I just have some stacked decks there, a beastiary orb and a few simulacrom splinters

These slots make Currency tab really good for "first tab", to dump everything there. If you have all premium tabs purchased, simply vendor everything that doesn't go anywhere (eg. rares, q20 gems, and uniques you already have).

Edit: maybe keep the Maven invites and watchstones though.