Rift Balance: Killer Vs Survivor
The 1st rift and the current rift tended to force players to play a specific role more than they would prefer. I've heard the argument made that the survivor challenges are intended to take longer because you need more survivors than killers for lobby match times to be appropriate. That's a valid argument. It really is. But consider that during times when the rift isn't a factor that lobby times are reasonable with survivor lobbies actually taking longer than killer lobbies on PS4. So obviously under normal conditions there isn't a survivor shortage.
This brings me to my recommendation. I think there should be 30% killer, 30% survivor, and 40% player's choice challenges per rift tier. That way at least 70% of a player's game time can be spent on their preferred role while working through the rift. This would certainly make players happier without messing up game queue times very much if at all. Player's choice challenges would just give the player a killer or survivor challenge that take the approximate same amount of effort to complete.