However, I current features announced for RoS have left me slightly underwhelmed. I simply don't feel the same need to pay $40 for it. To be fair, let's look at the proposed features for RoS as they currently stand:
To really motivate me to go out and buy the next expansion, I think at least one more unique class should be added.
I would really like to see some sort of Rune Words-esque system put in place, though it would probably need to be called something else to avoid confusion for the already existing Rune system.
Charms and Relics would also be nice, but measures need to be taken so that they don't take up so much inventory space, whatever happened to the proposed "Talisman" idea?
The mystic could be more useful by somehow integrating the talisman/runeword features into her.
I also really want to see massive amount of items added in the form of sets/legendaries/class-specific items, and have better use for uniques and rares.
TL;DR: Make RoS blow people away the way LoD did. The best way to do this would be to add another class, runewords, and charms.