i dont really think it can get better over time due to the way the game is set up...its a button masher. you get your mission and go.
what i would have liked to have seen them do,
say for the villians side of things....
you get to plan your own missions....make it so you buy plans from vendors,
so you start with bank heists at first to build up capital so you can buy bigger plans....
leading up to building a nuclear device, or a deathray or superman clone or what have you.
so you have missions that lead you to getting parts....once you get the parts, you can assemble your world ending device...and you have an end mission to plant that device....along the way you have heroes trying to stop you, depending how deep you are in the mission factors into which heroes your fighting....say booster gold, or blue beetle at the begining, leading up to batman or superman for the final missions..
then give the ability to team up with other players who maybe have a part you dont, combine together in a league of evil, and try to defeat superman or whoever
and you could still have all the preplanned missions thrown in there as well, to build up cash and levels to fight the higher up heroes.
it gives the players the feeling of being more in depth in the story, a hand in the action, and would make players more interested in coming back to play again,
as it is now i wouldnt pay a monthly fee to play what they have set up...