that's why there are unupped and upped tournaments dear sir(?), i have like 9 or 10 upped cards only, and i have already played (and got crushed) in the first one of the year, you should check them, even if you don't have an awful lot of things.
except if you're going against shards, then you need shards too.
and almost any upped decks can farm bronze effectively, it's just that all those you saw can farm it like they are AI 0 haha