I am not a long time Nasuverse-player. However, I have played plenty of other card games, and I really only have one concern about Nasuverse. It is, however, quite big.
It's the lack of a metagame.
Nasuverse, in its current state, does not have a metagame.
A metagame is not just "this is a good deck". A metagame is not just "I dislike facing the students deck". The term itself says it. It's a game about the game.
Since Nasuverse has a lot of moderators who can freely change cards, as well as no real policy on when to change cards, coupled together with the lack of a serious tournament structure, it has never truly had a metagame. People has never had the incentive to make the most efficient deck that beats all others - In some part due to the design of the game, in bigger part due to the lack of a metagame.
The part about design is that Nasuverse is highly class-based. There are a lot of cards that only care about an extremely small subset of cards. Playing a card that destroys servants is pointless unless you expect to face decks filled with servants. However, there's no such thing as knowing this in Nasuverse, because...
There's no metagame. People play what they deem fun for the minute, and all sorts of themes are represented among the main decks among a lot of the players. Since there's nothing to really lose if your deck is bad, it doesn't matter if your deck can beat other decks. It doesn't matter that you put in six more cards that you like, even though it makes your deck worse. It doesn't matter to you because it doesn't matter to anyone. It doesn't matter to anyone because there's no structure.
My proposal would be this:
Implement a seasonal structure of the game. By this I mean the following:
- A structure where in the winners are rewarded more than the losers.
- A period where no cards are added, changed or removed, followed by an evaluation of the results of the structured play, with a overhaul, addition and removal of any number of cards.
The benefits of this would be that since there's a reward for being good, you have an incentive to make good decks. With an incentive to make good decks, there's an incentive to make decks that beat the good decks. And with that, an incentive to make a deck that beats those decks. And so on, and so on. As well, when the time comes to make balance changes, you have actual strong data to base the changes on. The problem with Nasuverse, or more precisely, Kaoru's changes to it, was that Kaoru really had nothing to base his changes on. He could only change what he saw being played, what he percieved as strong or weak. Since no one could make a list of cards and say "these are the cards that win all the matches", he had nothing to go on except gut feeling. A seasonal structure remedies all this.
A tournament structure would be better if it was officially implemented into the Dulst-engine, but it doesn't have to. With a community this small, it would be easy to have a forum topic with tournament match results and so on.
Essentially, my point is this: If the game stays in the quite-casual manner it is right now, it is going to become boring a lot faster than if there were incentives to be competitive.