Trying to understand Ranked Placements

I am trying to wrap my head around ranked placements right now. I have spent the last couple days doing ranked placements and I honestly feel like support players get sh*t on. I did 10 matches as Support (mostly bard and maokai).

10 matches 8 wins 2 losses every match A- rating or better (3 S ratings) the loss matches I got C+ and B- ratings every match my K/D/A was good for a support (more deaths then kills usually but assists were high)

after completion of 10 games I get placed Bronze V.... wtf

Whereas on my alt account I played mostly Jungle and Top for 10 games

10 matches 7 wins 3 losses most ratings A and B K/D/A was mostly good with a couple unimpressive matches

after completing 10 games I got placed Silver IV... wtf

extreme bias toward non-support/champs who get kills?

I enjoy playing support role, and understand the general need we have of people who enjoy filling this position but I am seriously upset about this.