The way I see the OP is that the problem is in the item generation tables. To simplify, we're looking for HGEs with proto alloys, but only finding the ones with proto heat radiators. And so the problem is that there are so specialized things you need to look for randomly... if there was a couple alloys swapped into the heat radiators (and vice versa), then when you find the wrong one, you might still be disappointed, but you're also making progress. And that changes things a lot in the experience... there is no grind when you're not making progress, it's just a lottery where you're waiting to win (and you might not). Grinding would be better... doing the same thing again and again and getting some progress each time.
That's why people look to lowering the exchange rates for up and cross grades at the material trader... that helps make things into a grind, because requiring less means that more often a drop gives you something that you can consider progress. But it's not really the only way to solve the problem. Personally, I think the biggest problem with the material traders is that they're a bandage on a system that has more fundamental problems... and the OP is an example of that. There are simply too many levels of materials and grades of modification for the system to work well... the RNG and item generation suffers because of that, and it's very easy to keep getting the wrong ones because there's so many types, and so first there's a bandage of increasing drops to sets of three and now another with the traders. But, if there was just chemical whatsits and heat thing-a-bobs without there being five different types masquerading as levels of them things would work better to begin with. But failing fixing the core issues, you need systems that guarantee the player gets some progress for an amount of time put in... better ways to get specific materials or just increased diversity in drops.
I too have spent an entire evening hunting a material and not finding any of it. It was a very common material though, and although the material traders would now solve my problem (in that I was getting lots of "grades" too good to use, because they're separate things), it doesn't address the actual problem... a material listed and intended to be very common was being dropped at a rate that made it rarer than very rare in drops with materials in its class. Which again comes back to my issue with material traders just being a bandage on the system... it allows for the hiding of a behaviour that's wrong to the point of buggy.