Not sure if this has been mentioned yet but:

Removing all the annoying screen spams such as player 1 has killed player 2, sometimes i get that spammed even after i leave game and join an instance lol.. kinda stupid
- just leave in it chat, instead of spamming it in my face everytime someone gets a kill.

Or the "player 1 has joined game or red/blue team" especially in the middle of a running game... you get a huge lag spike everytime someone joins..
- same as kills, show people have joined game in chat