Well, that's not really a problem in the game, but a problem in either your perception or the community.
The topic of this thread is that "EtG gains curve favors older players." However, there is absolutely no problem with this. In fact, is there even a game where killing higher-level mobs nets less exp-per-minute for higher-level players? RPGs are supposed to get easier as you play, lest there would be no reason for grinding, and it would not be an RPG. This is the same with balanced CCGs.
Silver, AI3, and maybe even PvP1 net more electrum than AI4. Even if you choose to farm AI4, adrenavamps is a pretty slow (compared to rushes) and fragile (compared to Mono-Aether). Maybe you're just farming on the wrong things, or with the wrong decks?
As for there being multiple decks having upgraded cards, this is because upgraded decks are simply better than unupgraded decks (obviously, this makes sense and should not be changed). When a veteran posts a deck that can grind better than previous decks on the forum, he aims for the largest group of players in the community. This is not the group with all the nymphs or the group with no upgraded cards, but the group that can easily obtain upgrades and non-nymph non-mark rares. That is why there is a greater amount of upgraded decks on the forums.
However, this doesn't mean that the unupgraded decks on the forum are sub-par. There are some very efficient unupgraded grinders floating around. While, as expected, unupgraded decks are not as good as upgraded decks, the only reason a veteran would not post a more efficient unupgraded grinder on the forums is because he is spending his time developing upgraded grinders or because the better alternative for the most efficient grinder currently on the forums simply does not exist. Either instance is not a problem in the game.