Is it really that hard to type "/mute all" at the beginning of each game?
In saying this, muting everyone on the server isn't a solution at all. It's more of a "applying a sticky plaster to an arterial bleed" kind of fix.
I know that the server is toxic (every server is), but wanting to mute all the players gives a little insight into your own state of mind towards the game. It shows us that you are at a point where you are a little tilted at the beginning of each game, due to your low expectations of your teammates. Even though your match history shows that you are playing really well, you could probably play even better if you get rid of this dark cloud.
Playing with friends (that you know aren't toxic) is the best fix. I see you already have been playing some premade games, and you can always expand your circle so you never have to play solo/duo again! Take a look over on the team recruitment boards and see if there are any fellow aram mains needing a friend. If not, post your own ad and specify that you don't want toxic players. You can even create a non-toxic aram club, so you will never run out of people to play with (you can also kick toxins from the club).
In terms of playing on the PBE, I would suggest sticking to custom/bot games to avoid the toxicity. Either that or try and find some nice people to play with on there as well.
If you do encounter a negative player, be sure to report them as every report counts!
As you probably know, Riot has a number of player behaviour systems in place that you can read about HERE
On top of this, a tribunal is currently being worked on as confirmed HERE
If you are worried about the toxins afk and ruining your games, there is also the leaverbuster system that you can read about HERE.
Good luck in your future games ♥
