Gold means your average, but I believe that 15-25% range is above plat/diamond.
Funny when people pull rank on me, I was 50sr shy of Masters last season but got fucked so hard that now I'm maining defense heros and got placed in Plat. I grinded from Gold to Diamond in S3, but I'd rather play in low levels because at least I can have fun, and not get buttfucked by one-trick DPS and Mercy mains.
As a Pharah main, Mei and Junk are easy to play. I play Sym sometimes because I consider her a defense hero. Then Bastion as a hitscan.
When I dropped from Masters, it was because I got 2-3 Mercy mains each game and they couldn't play anything else.