Ranked Zombie Mode unlocking difficulty stages should be changed.

xkennyPLx

Currently, anyone can reach high difficulty stages by getting placed in a group of people that can carry them through the match. This means that people that queue for random matches in higher difficulties will constantly get matched with players that can't contribute enough damage to complete the match within the time limit. I can't progress because inexperienced players keep queuing for matches that they can't do anything in.

Instead, for future ranked seasons, unlocking difficulties should be done by reaching DPS thresholds, rather than completing matches.
In example, if you can consistently deal 6,000 damage per second during the match, you'd be able to unlock the 7th stage difficulty.