Oh it is relevant , you can only have a good risk/reward system if your game is working probably. That said a good, a risk/reward doesnt have to be 0%/100% , like many allready said, haveing a checkpoint system would work perfectly and an as extra idea, increase the rewards chance for the good rewards for every A-C roation as an extra for real endurance runs to make sense for more than the hardcore 9999 grinder.
Firstly Sorry, while you were not the first to speak about endurance, you were the first that came with the point that endurance only makes sense when you lose everything on mission fail.
My intention was not to step on your feet or anything like that, i just know that endurance runs need a whole lot of love and changes to make them more interresting, thats was not to say that you cant talk about them , just that the main focus isnt on endurance alone.
As for circuit, while yes it is some kind of endurance run. (even if more of an easy one) The reason its in the titel is because it follows the mission structure of an defence. Missions like survival are not even a problem for me because you can leave them the normal way, the risk of losing everything is close to 0 in survival endurance because you can leave anytime. Defence and circuit dont have that.
As and extra for the "making better players" i have 10k cleared missions and 151 failed and i can say with 100% certainty that around 140 of them are lost to bugs and glitches, many of them are from the early open beta. Warframe is 99% of the time not an hard game.