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Hunters terrify me in Arena probably more than anything in the sense you always have to play around UtH by never over-committing to the board. Playing just one big minion on curve a turn has always worked for me against Hunters.
So with personal Arena experience and after watching a decent amount of streamers, the amount of wins does not have THAT much to do with the amount of rares/epics/legendaries.
Those are the real priorities, so a lack of those will make winning nearly impossible if you try to trade card-for-card.