AFK Players and griefers
Well you can report them. Look at the scoreboard, go to their name and the option should be there. Sadly that's the best thing that can be done really. Griefers are an unfortunate yet typical occurrence. As for AFK players...it's frustrating but I try to give them the benefit of the doubt (for the sake of my own sanity) and figure that maybe they are being bothered by something at that very moment IRL or lag or whatever.
It's difficult to do anything about them really. Report systems are easily abused so in a way I'm glad they are practically meaningless as they are at the moment.
If someone simply doesn't like another player or they blame their team for their own misplays constantly, there will be a lot of unwarranted reports which is essentially what's happening right now
Same as what's been said above with people that go AFK generally speaking, I think benefit of the doubt is fair.
People will troll and throw and jump off the map with or without punishments. It sucks a lot but it happens in every game and there's not really a consistent way to deal with it without hurting innocent players by abusing the system.
I think the worst for me personally and something that occurs more in this game than most due to how team oriented it is, is the toxic mentality of a lot experienced players. They go into the game with the mindset that they are above everyone else and they will flame the chat or throw the game if one thing goes against them, winning or losing.
Playing with new players can be frustrating at times but it happens to all of us unless you stack and literally beat them out of continuing to play the game.
I think a Casual Queue would be healthy for the game, similar to how quite a few multiplayer games operate. If your profile level is below 20, you will only match against below level 20 players. I think there's a fairly healthy split between new and experienced players so queue times won't be affected too much. It gives players a chance to get to grips with how the game works, rather than being tossed in to make the numbers up in a game filled with experienced players where they learn nothing but get frustrated, and probably get flamed by the many experienced toxic players.