I don't see the problem you gained 12 lp that's just a result of a bad mmr
If you can see, he has 66 LP instead of 0, so obveously he doesn't have too bad of an MMR and plus he did win that game. I can see the frustration and I agree, they probably do need to look at it again.
Bump, ive now won 10 games in a row and got to diamond 4, and I got 12 or 14 lp for my first win in d4. I'm also playing with players around my rank.