one of the biggest problems is that its deciding that based off the fact that so many champions you have played have 6-7 deaths per game 1-2.0 kda may not sound to bad to you, but to the game it thinks that you have been getting lucky. You have decent kda on graves I don't know how that will last I just came from bronze 4- silver here the other day.
doing duo q inflates the mmr of your team so the lp you gain reflects the opposite your actually playing with bronze 5 players and not people of your own mmr so when you lose a game against bronze 5 it severely harms your mmr If you look at the people your playing against you'll notice almost all that you've played are bronze 5.
If you continue playing graves and dodge a few games you don't feel you want to play you'll get out of that; although bad it won't hurt your mmr
it's really important though because if you get a tripple q of players with .2 kda per game with 10 deaths each game then figure your team will most likely be down atleast 9000 gold and unless you know you can make that up then it's best to dodge
p.s this thread should be in general discussion. but I hope i helped solve your problem