I have no idea on you have ever balanced the Mission Buff for endless run, but I know you really dislike the endless run mission. However, these missions consist the most weapon,warframe operation time and the riven mods deal. Maybe, we can add some buff only can get in mission for the tenno when they finished one stage or the C stage , like rougelike games done, when they get out the buff goes away.
I got this idea ,due to you have already done some buff to the missions (the steel path, the Arbitrations,and the endless run Void Fissure mission) Actually, we can get a +25% ??buff in void fissure when the ralic opened, i pretty like it. If we change how the buff acting ,not for the resource getting , to directly buff the Tenno and their enemies.
Maybe Tenno can get buff like range up,strength up, duration up but range down, or need moving or parkour to powerup their warframe or weapon, kill with gun let the body boom. We got this buff from mods and Arcanes. If we can get these pretty buff in mission that will be nice, for limited Mod slots we need to choose. Before Tenno choose their rewards and buff, their enemy get some random buff like damage up, speed up. To change the game strategic, or stop some Tenno from AFK, let them take guns to shot.