Making the tower relevant post lvl20 (gunsmith, shader lady)
Noticeboard in tower for random group forming
More diversity in rarity of gear. (Rare at lvl20 is not rare, it's standard as no green or white gear exists)
Weekly PvE and PvP events. There should be a choice at all times depending on what floats your boat
And lastly, i'd really like more missions/stories to be added at intervals. DLC only is a bit of a cop out compared to how they marketed the game on having "new content everyday". And no, the daily heroics do not count in my book!
Still love the crap out of this game though!