Improvements:
More quests and epic quests.
More Daily resets.
It is possible to buy cashshop items without using real $.
Max lvl for secondary = 50, so you can swap pri/sec classes if its not too late. (eg. you went mage priest, but decided to go priest mage instead, its possible if u didnt waste too much skill points)

PvP: Pretty much the same.

Community: I play on US pvp server, there are often pkers around mid-lvl areas.

Lag issues: None for me in Asia.

Build: No idea, try it

Balanced?: No. Cashshops are not meant to balance a game.

Content rewarding?: No idea what you are asking.