Matchmaking

Is the matchmaking mmr based or does it match u will players of "similar skill"? I just did my 10 placement matches and in almost all 10 matches I was top dmg on my team and the only person with a k/d of a least 1.0 (not including the supp, but still the only 1 if u do count the supp). I keep getting people that go like 2/10 or 8/15 with terrible damage.