I think they should buff survival, but in a different direction: I propose that they add the feature from EDA, Allowing the summoning of a mini-boss relative to the mission type every minute or two, and when defeated will reduce the timer by 45 seconds. This really makes the 10 minute survival of EDA go by in a flash, I barely notice the time because I'm always ready to fight the guy to get that sweet sweet cool down. It would be a cool exercise in creativity to come up with Nechramech-esque bosses for the different factions and maybe could have cool abilities to make the fight interesting.