Like I said I think individual play should have some influence on how much your rank increase or decreases, but I don't think it should get to a point where you can rank up for losing. Solo queuing is and always has been a gamble and rather than complain about going down a rank because of terrible randoms you should look into getting some people to play with. If we get to a point where individual play has too much direct influence on your rank it basically turns into free-for-all with two teams where getting a high k/d yourself is favorable over playing for the team.I don't actually like basing it entirely off of winning. Yes it's a team mode, however its team slayer. If someone gets 15 deaths and 1 kill yet their team manages to win, why should they rank up? I think there should definitely be a bonus for winning and the opposite for losing, however if you play exceptionally well and still lose I don't think you should rank down. It's not your fault if your team sucks.
My preferred system would be:
Win = +25
Loss = -25
This is added to the amount of points you get for how well you played.
If your skill nets you 30 points but your team lose you only get 5 points.
I would also make it so those who do really badly get negative skill points. If someone gets -30 skill points but their team still loses they are still punished for being awful.