Seems like the only thing going on is that you are burning yourself out on this kind of content, and that you need to take a break from it.
There is no evil RNG manipulation master plan. There is only people getting good and bad luck. For example, unlike you, i did never get an "amazing" RNG in the beginning of the new maps, and i sure don't get a better luck with the thief maps.
People are complaining that there is nothing to grind and that there is no long term content in the game. And when they get that, they ask for it to get nerfed so they can be done with their 20 achievement clears in two weeks. So that they can complain again that there is nothing to grind and nothing to do ?
Even if i don't get to the final room, i still get a lot of gils from running the maps, and that's not really compatible with another supposed evil master plan to limit how rich we become. If it isn't the case for you, maybe it is because you are too slow to run the maps. The speed you are going on is an important factor. Of course you are not going to get the same amount of gils from a speed run "FFA bring 3 maps each" 8 players group, than from a chill run with your FC members where you are going to take a lot of time joking and talking between you, and waste even more time remembering whose map it is because it is owner need and others greed. When i am going in the second type of group, i sure don't expect the same gains than from the first.
The gem to get the mount is still really worth it with its 3 millions price on the market board (at least on Light). If the RNG gets better like you are asking for, its price is going to get way down, and then people are gonna complain that there is really only trash drops to get.
Asking to make these maps worth running before the next map dungeons release would have make sense when the two kinds of maps (dungeons and wheels) were still on the same kind of maps. If you were then late on maps completion, you would indeed get and additional layer of RNG added to the entry portal, making things more difficult. But it doesn't make any sense to ask for that since dungons and wheels are now splitted on two different kind of maps. The future wheels will very obviously gonna be put on exclusive living memory only maps, like we did get for the elpis ones.
I might have forgotten one point or two, like recruiting members being heavily dependant on what time of the day you do it (during meals usually bring me bad results), but in short there is so many things wrong with what you are saying that it is obvious that you have more of a beginning of burn out problem than anything else. Just take a break from this activity and do some maps again when you will feel like it. Don't end up like these people i did see quitting the game because they did force themselves way too much on a kind of content they were not enjoying anymore.
And by the time you clear a dungeon, you could also get the other kind of supposed cluster streak you are trying to get or avoid. Or if you are in a supposed bad streak, the next try could also be bad, or suddenly switching to the begining of a good one. Stop trying to find logical explanations to what is only good or bad luck, and just spam more maps XD