Getting to Mythic isn't that hard but staying there is.
52% win rate isn't good but I guess you hab bad luck with starting hand and drawings. Happens to me too. RNG Gods aren't always on our side. God damned! 😂
Your selection for card to switch seems reasonable and on point. I would do the same. Since I reach Mythic more often now I check the top card decks on GUdecks to see how are the Meta changes.
Keep up the work and good luck in the matches.
May the RNG Gods be with you!