well, a 55% winrate-deck is only an average. higher legend people might go from rank 5 to legend with 70~80% winrate where as others have a 45% winrate with them.
So yeah skill and knowledge isn't everything but it sure isn't nothing.
The more games you do, the more your total RNG will go to the middleground of having 50% positive RNG moments and 50% negative RNG moments. You just happen to remember unlucky events better than lucky moments.
From personal experience: (reached legend with galagrond rogue on my phone) (Excuses for my English, not my first language)
-Might be coincidence but i found the opponents weaker at the end of the month than the beginning of each month (maybe because the best players are higher in legend already?)
-Identify your opponents deck and make a game-plan in the first few turns (like counting the amount of boardwipes or bombs your opponents deck still has in them)
-I played ranked till i had 5 loses total or 3 in a row then i took a break and do something else. This worked for me personally since i get annoyed easily if i get on a lose streak and thus performing worse, every answer your opponents plays seems unfair and you get worked up more and more. The tough part about is that you exit the game with a lose as last game :P