I hate to say it, but I think you're being a bit too focused, and that's making it a chore for you. Engineers can be rough if you fire up the game one day, decide to get DD5s and then work your way down the ingredient list, jumping through hoops for the stuff.
Engineers can be rough for many reasons. One of the most well known reasons is that RNG is not working properly, or in a way that makes sense, since the beginning of time. That's why many ppl suggest to "just play the game". I have many hours invested in "just playing this game": if RNG had been doing its job, you'd think I would have plenty of mats in storage by now and wouldn't even need to search for them. But that's not the case for me and many other who posted the same complaints. Because of that, you eventually end up having to search for a material or two for engineering (if you have been lucky). When that happens, you are at the mercy of the RNG gods.
The design is faulty: it's hard enough to find HGE, for example, where multiple conditions have to be present (system with High Pop, in Civil Unrest, Independent, not mixed with other states or alliances, throttle at half speed or whatever, 500ls from the main star, etc...etc...etc...) but you also have to be lucky enough that the right material will spawn and that you won't be ambushed (once in the HGE) or interdicted (on the way to the HGE). This design make it possible for a player to end up without the mats he/she was looking for, after an hour or two of play: this is the worse thing you can do to a player and sure to bring frustration. In other words: if a player finds a yellow box, spawn gold coins; not "if a player that happens to jump 3 times while flipping in the air while alternating a raspberry with 3 real farts, finds a yellow box, spawn one of the three following things: (insert three random thing here and make it possible that those 3 things are not what the player was looking for). I think a player should always be rewarded in a game for time invested and effort, one way or another, if you want to have a good game design that will make ppl want to come back and play more. Oh, and we don't have the capability of selecting multiple filters in the galmap to find those conditions btw.
Also, the fact that they came up with material traders is to me a testament that FD have acknowledged that RNG has a problem and the way they are trying to fix it (ie material traders) tells me that RNG cannot be fixed properly without a complete rewrite perhaps?.