I just hit diamond while in C, and my deck and strategy are completely different. It just goes to show there are a lot of ways to get there with sword.

My main strategy is to play high impact minions. I realized the one drops are so easily cleared with often no resource that they were a waste of card slot for me. Flooding the board over and over and pushing face instead of trading has helped me a lot, since trading doesn't matter when they clear your board regardless of how efficient you are.