Not to sure what it is that died on this one.
I did enjoy it and bought the premium partly more on the edge to support the series.
If there's another series I wonder if you could get a story mode involved.
Which I mean a real campaign where what you do changes the flow of game play.
At the end it would open up hybrid classes which would make the premium content much more enjoyable. As well as unlocking a set of new classes to use.