1.
Casual CC: Solo queue only, random teams.
Ranked CC: Pre-made PvP teams. Queue only as a group.

2.
Allow players to chat. There is no reason to not be able to speak in CC when you can speak in Frontlines. Players would rather be able to speak, and possibly have to report a toxic player, than to be spammed with quick-chat macros all day, while simultaneously not being able to properly communicate. This would also allow the deaf community to communicate during ranked matches when they can't hear their team mates in Discord.

3.
Add diminishing returns.

4.
Do not allow 2 tanks, or two healers, or two tanks and two healers to be on the same team. Limit teams to 1 tank, 1 healer per team.

5.
I'm not sure if this last one is possible: But while it doesn't affect PvE very heavily, the tick rate of the server absolutely affects PvP tremendously. IF it is possible to fix the tick rate, now is the time to do so. If it CAN be done, it absolutely should be done.