>>529814797
Weird, I'm Sapphire B1 and have more balanced opponents. Going back as far as the game lets me, and only counting Ranked, it's
7 Portal
6 Sword
6 Rune
6 Haven
2 Dragon
1 Forest
0 Abyss (that one match showing up in the pic was private)

That's also my experience in general. Abyss is the rarest, followed by Forest and Dragon. Beyond that, it's very even, though there's always more Portal than anything else.