Sometimes these LP gains make 0 sense. I recently made it into B4. Played 4 games since then. Won first two. Gained 12 LP for each of those. Lost one game and lost 23 lp. Won my next game in a 4v5 and gained only 7 lp.
My MMR must be really weird or something.
Maybe your team MMR was a lot higher than the other team meaning you were predetermined to win which would cause you to win less LP
LP gains are determined off of your individual MMR in comparison to your team and the opposing team's MMR. It has nothing to do with how well or how poorly you do. It has nothing to do with whether or not it's 5v5 or 1v5. The only thing that matters is winning or losing. So you'd have to look back at your team's average MMR and the opposing team's average MMR.
