When a few cards are completely dominant, it means you either play those cards or you lose, which makes the meta stagnant. A Healthy meta is one where tons of different decks are viable and the highest level of play. As it is right now, Ramp decks are, in general, the strongest since Ulamog is the strongest card in the game and can, effectively, be run as a 3-of thanks to tutoring with From Beyond.I don't get why they'd remove the cards instead of actually fixing the problem which is the whole sets for the expansions aren't there for the sake of "balance." I mean the previous Duels also had a problem with a few cards absolutely dominating or people using a certain deck (09/"Duels '11" being Elves) abuse. I don't get how changing these cards is suddenly gonna stop people from finding new cards to abuse in the "meta."
Putting in every card from the set isn't realistic. Certain cards would take a lot of extra work to program for little gain, like The Great Aurora, for example. Also, since there's no rotation, aggro and burn would just get progressively better and better as more sets are released.
The real issue is that, in regular Magic, what helps to balance the meta is the sideboard. Being able to tweak your deck against a specific match-up mid-match makes a lot of decks more viable.