The randomness of the riven is too harsh, the farm is frustrating and infuriating, theses rivens are suposed to even out less used weapons to the most used one, but to get that you need tremedous amounts of kuva (if you dont have luck) to get a average roll and thats not fun and a enjoyable thing to do in this game, i don't want to waste my time on this system, but i HAVE to if i want to make weapon viable to the "end game" content so heres my suggestion to make this system less painful:
-Allow us to "lock" only the negative stats of the riven with a cost of extra kuva, getting a good negative is just as hard as getting a good positive stat, negating worst possible stats such as -damage -crit chance or -status chance, will not make a part of me die inside when i get a good positive stats but with a terrible negative.
-Reducing the price of the roll to 2.000 kuva, after the 10th roll, 3600 kuva per roll is just too much, is like asking for 100$ for a lever pull in the slot machine. -or-
-Make an "arbitration" type of mission for kuva, lorewise endo is suposed to be rarer than kuva and yet you get more endo through missions than kuva, after i started doing arbitrartions more consistently i get all my mods maxed out and i have more than 120k of endo just sitting in my ship, i dont need more endo but i always need more kuva because rivens are a kuva eating machine
Just to clarify i do not care about the riven market, its not suposed to affect the aspects of a system like this, the market will change and adapt like it always does