I don't know how I feel about the new champion masteries

I honestly suck at getting these new masteries. Unless I play these really good champs that super hard carry, I am finding it so difficult to get past an A with all of the champions I play. It's actually gotten beyond so frustrating. I generally play champions that are engage or tanky, and generally my play style champions arent decent at farming (i main jungle volibear) and usually get my other team mates fed. What I find super annoying is that by me getting 8 deaths on this champion, I won us the game by letting other champions cleanup? I dunno, I just can't seem to get the mastery, and I dont know what to do.