Sykar
Arcane
Well, you're kind of all wrong. Borderlands has a lot of completely random drops, but uniques come in mission rewards as a definite reward and certain mobs or bosses have defined drop pools, and the way uniques and legendaries work is by including a unique part that defines what set of parts can go with them while the "random" weapons do actually act the same way, but without the unique/legendary modifiers like specific spread patterns and such.
WF would be similar when you're grinding for warframe and weapon parts, except getting one single lucky drop isn't enough and isn't followed by a crafting and resource cost. That sounds bad but in the other hand shared and defined resource pools make the items who are crafted off those resources a lot more permissive than most grinding sims. That's why the open world areas' own sets of resources are such a massive grind, you've not been passively collecting materials for the hours of your life this stole from you.
Each Warframe alone needs 4 different blueprints most of which are random drop and quite often rare materials like Oxium which new players do not have in the quantities these Warframes require. Then there is the 72 hour build time which you can speed up via platinum only. Dual Weapons and unique Warframes like Equinox need even more. Often you will need 20-40 runs for the rare blueprints which can take quite a while so the total amount of runs can get up to 120 easily just to get a full set of bps.
Regardless how you want to spin it with meaningless details, both are grind heavy to get the best gear and both are highly reliant in RNG luck. Sometimes you get shit on your first run, sometimes you run something 50, 60 or a 100 times and still got zilch. Also many uniques in Borderlands were not quest rewards but drops which also had several variants. I could also say that the Relay quests which each planet has at least one off guarantees blueprints of all kind so there is an equivalent to certain unique/rare quest rewards in Borderlands.